<p>html需要实体字符来解决保留字符冲突、显示非键盘字符及防止解析歧义与安全风险；1. 使用实体字符可避免小于号、大于号等被误解析为标签；2. 可显示版权符©、注册商标®等键盘无法输入的符号；3. 通过转义用户输入内容防止xss攻击；对于命名实体与数字实体的选择，建议常用符号如、©使用命名实体以提高可读性，而对兼容性要求高或无命名实体的字符则使用数字实体如、&、"、’、 、©、®、™、€、—、–等；实用技巧包括：优先使用textcontent而非innerHTML以防止xss，后端输出时进行html转义，确保页面声明utf-8编码以支持更多字符直接显示，并借助w3schools等<a style="color:#f60; text-decoration:underline;" title="工具" href="https://www.php.cn/zt/16887.html" target="_blank">工具</a>查询实体编码，从而提升开发效率与网页安全性。</p> <p><img src="https://img.php.cn/upload/article/001/221/864/175463490664488.jpg" alt="什么是HTML实体字符？如何显示特殊符号？"></p> <p>HTML实体字符，简单来说，就是一种在HTML文档中表示特殊字符的方式。因为HTML本身会把某些字符（比如小于号<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>或大于号<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">></pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>）识别为标签的一部分，或者有些字符（比如版权符号<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>）在键盘上不好直接输入，这时候我们就需要用特定的编码来告诉<a style="color:#f60; text-decoration:underline;" title="浏览器" href="https://www.php.cn/zt/16180.html" target="_blank">浏览器</a>：“嘿，这里我要显示的就是这个符号本身，而不是把它当作HTML语法。”</p> <p>要显示特殊符号，核心就是使用这些HTML实体字符。它们通常以一个<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>符号开头，后面跟着字符的名称或其对应的数字编码，最后以一个分号<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">;</pre><div class="contentsignin"></div></div>结束。比如，如果你想显示一个小于号，就不能直接打<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>，而是要用<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>或者<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>。这样，浏览器在解析时就知道，这是一个要显示出来的字符，而不是一个标签的开始。</p> <h3> <a style="color:#f60; text-decoration:underline;" title="为什么" href="https://www.php.cn/zt/92702.html" target="_blank">为什么</a>HTML需要实体字符？它解决了哪些实际问题？</h3> <p>说实话，我刚开始接触网页开发的时候，最让我头疼的就是想在页面上显示一个小于号<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>或者大于号<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">></pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>，结果页面直接就“崩”了，或者说解析成了一个奇怪的标签。那时候真是百思不得其解，后来才发现，哦，原来这些符号在HTML里是有特殊含义的，它们被HTML“保留”了，用来定义标签结构。如果你真的想把它们本身显示出来，就得用实体字符来“欺骗”一下浏览器。这就是实体字符解决的第一个大问题：<strong>处理HTML保留字符的冲突</strong>。像<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>（和号）本身也是一个保留字符，因为它用于实体字符的开头，所以如果你想显示一个<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>，也得用<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>。</p> <p><span>立即学习</span>“<a href="https://pan.quark.cn/s/cb6835dc7db1" style="text-decoration: underline !important; color: blue; font-weight: bolder;" rel="nofollow" target="_blank">前端免费学习笔记（深入）</a>”；</p> <p>接着，我们还会遇到一些键盘上根本没有的字符。比如，你想在网站底部加上版权信息，需要一个<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>符号；或者显示注册商标<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">®</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>、欧元符号<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">€</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div>等等。这些字符，你总不能指望用户都能正确输入，或者说不同<a style="color:#f60; text-decoration:underline;" title="操作系统" href="https://www.php.cn/zt/16016.html" target="_blank">操作系统</a>的输入法都能完美支持吧？这时候，HTML实体字符就成了救星。它们提供了一个<strong>跨平台、跨编码的统一表示方式</strong>。无论用户用的是什么系统，只要浏览器能识别HTML，就能正确显示这些符号，大大提升了内容的兼容性和可靠性。这解决了<strong>非键盘字符的显示问题</strong>。</p> <p>还有个比较隐晦但很关键的问题，就是<strong>避免解析歧义和安全风险</strong>。特别是当你的网页内容是动态生成，比如从数据库里取出用户输入并显示出来时。如果用户输入的内容里包含<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><script></pre><div class="contentsignin"></div></div>这样的HTML标签，直接插入到页面中，就可能引发跨站脚本攻击（XSS）。而如果我们在把用户输入的内容插入到HTML之前，先对其进行HTML实体转义（把<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>转成<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>，把<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">></pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>转成<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">></pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>等等），就能有效阻止这些恶意代码被浏览器解析执行，大大提升了网站的安全性。我个人就踩过这种坑，所以现在对用户输入的内容处理格外小心。</p> <h3>命名实体与数字实体，我该如何选择？</h3> <p>在HTML实体字符里，我们通常会遇到两种形式：命名实体（Named Entities）和数字实体（Numeric Entities）。</p> <p><strong>命名实体</strong>顾名思义，就是用一个比较好记的名字来表示一个字符，比如<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>代表<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>，<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>代表<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>，<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"> </pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div>代表不换行空格。它们的好处是<strong>可读性非常强</strong>，你一看就知道它代表什么。对于一些非常常用且有清晰语义的字符，我个人倾向于使用命名实体，因为这让代码看起来更“人性化”，后期维护也更容易理解。比如，我写版权声明的时候，肯定会用<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>而不是<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>，因为前者更直观。</p> <p>然而，命名实体也有它的局限性。首先，<strong>不是所有的特殊字符都有命名实体</strong>，或者说，有些命名实体（比如<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">'</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>代表单引号）在某些旧版浏览器中的支持度不如数字实体那么好。其次，有些命名实体可能比较长，输入起来反而麻烦。</p> <p><strong>数字实体</strong>则是通过字符的Unicode编码来表示，分为十进制和十六进制两种形式。十进制形式是<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&#十进制数字;</pre><div class="contentsignin"></div></div>（例如<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>代表<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>，<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>代表<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>），十六进制形式是<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&#x十六进制数字;</pre><div class="contentsignin"></div></div>（例如<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>代表<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>，<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div>代表<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>）。数字实体的最大优势在于它们的<strong>通用性和精确性</strong>。因为它们直接对应Unicode编码，所以理论上可以表示任何Unicode字符，而且<strong>兼容性极佳</strong>，几乎所有浏览器都能正确解析。</p> <p>那么，我该如何选择呢？我的经验是：</p> <ul> <li> <strong>对于那些非常常见、一眼就能认出来且有清晰命名实体的字符</strong>（比如<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>, <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">></pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>, <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>, <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">"</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>, <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>, <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">®</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>, 不换行空格等），我通常会选择<strong>命名实体</strong>，因为它们让代码更易读。</li> <li> <strong>对于那些不常用、键盘上没有、或者没有明确命名实体的字符</strong>（比如某些数学符号、特殊标点、或者需要确保在所有环境下都能正确显示的字符），我就会毫不犹豫地去查它的Unicode编码，然后使用<strong>数字实体</strong>。特别是当我在处理一些从外部系统导入的、可能带有各种奇奇怪怪字符的数据时，数字实体是我的首选，它能提供最稳健的保障。</li> <li> <strong>对于单引号<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">’</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div></strong>，虽然有<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">'</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>这个命名实体，但因为它的兼容性问题，我更倾向于使用<strong><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">’</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div></strong>这个数字实体。</li> </ul> <p>总的来说，命名实体是方便可读的快捷方式，而数字实体则是更底层、更可靠的“万能钥匙”。</p> <h3>哪些常见特殊符号是开发者经常需要处理的？附带实用技巧。</h3> <p>作为开发者，我们日常工作中经常会遇到并需要处理的特殊符号及它们的实体形式，主要有以下这些：</p> <ul> <li> <strong>小于号 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div></strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div> 或 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>。这个是最常见的，因为它是HTML标签的起始符号。</li> <li> <strong>大于号 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">></pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div></strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">></pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div> 或 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">></pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>。同样重要，是HTML标签的结束符号。</li> <li> <strong>和号 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div></strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div> 或 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>。因为它是实体字符的起始符号，所以它自己也需要被转义。</li> <li> <strong>双引号 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">"</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div></strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">"</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div> 或 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">"</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>。在HTML属性值中如果需要包含双引号，就得用它。</li> <li> <strong>单引号 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">’</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div></strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">’</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div> 或 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">'</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>。<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">'</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>在旧浏览器中支持不好，推荐使用数字实体。</li> <li> <strong>不换行空格 ` `</strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"> </pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div>。这个非常实用，它不仅表示一个空格，还能防止浏览器在该位置自动换行。在需要多个连续空格，或者想让两个词强制保持在同一行时特别有用。</li> <li> <strong>版权符号 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div></strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div> 或 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">©</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>。网站底部版权声明必备。</li> <li> <strong>注册商标 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">®</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div></strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">®</pre><div class="contentsignin"></div></div> 或 <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">®</pre><div class="contentsignin"></div></div>。</li> <li> <strong>商标 <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">™</pre><div class="contentsignin"></div></div></strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">™</pre><div class="contentsignin"></div></div> 或 <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">™</pre><div class="contentsignin"></div></div>。</li> <li> <strong>欧元符号 <div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">€</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div></strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">€</pre><div class="contentsignin"></div></div> 或 <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">€</pre><div class="contentsignin"></div></div>。</li> <li> <strong>长破折号 <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">—</pre><div class="contentsignin"></div></div></strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">—</pre><div class="contentsignin"></div></div> 或 <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">—</pre><div class="contentsignin"></div></div>。</li> <li> <strong>短破折号 <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">–</pre><div class="contentsignin"></div></div></strong>: <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">–</pre><div class="contentsignin"></div></div> 或 <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">–</pre><div class="contentsignin"></div></div>。</li> </ul> <p><strong>实用技巧：</strong></p> <ol> <li> <p><strong>JavaScript中的<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">textContent</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>与<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">innerHTML</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>：</strong> 当你需要将文本内容插入到html元素中时，如果这个文本可能包含HTML特殊字符（比如用户输入），强烈建议使用dom元素的<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">textContent</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>属性，而不是<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">innerHTML</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>。<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">textContent</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>会自动对特殊字符进行HTML实体编码，确保它们被显示为普通文本而不是被解析为HTML标签，这能有效防止XSS攻击。而<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">innerHTML</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>则会直接解析HTML字符串，如果字符串中包含恶意脚本，就会执行。我曾经就因为直接用<div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">innerHTML</pre><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div><div class="contentsignin"></div></div>插入用户评论导致页面出现问题，后来才意识到这个安全隐患。</p><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class=’brush:JavaScript;toolbar:false;’>// 假设 userInput = "<script>alert(‘xss’);</script>"; let div = document.getElementById(‘myDiv’); // 安全的做法：textContent 会自动转义 div.textContent = userInput; // 页面显示：<script>alert(‘xss’);</script> // 危险的做法：innerHTML 会解析执行 // div.innerHTML = userInput; // 页面会弹窗</pre><div class="contentsignin"></div></div></li> <li><p><strong>后端或服务器端转义：</strong> 很多时候，数据是从后端数据库获取的，或者通过API接口传输。在这些数据被插入到HTML页面之前，通常需要在服务器端进行HTML实体转义。大多数现代Web框架（如python的django、flask，Java的spring，Node.JS的express配合模板引擎）都有内置的模板语言或函数，可以自动进行HTML转义，以防止XSS攻击。这是在内容输出到前端前的第一道安全防线。</p></li> <li><p><strong>确保文档字符编码为UTF-8：</strong> 虽然HTML实体字符能解决很多特殊字符的显示问题，但更根本的是要确保你的HTML文档使用UTF-8编码（在<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><head></pre><div class="contentsignin"></div></div>标签中添加<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><meta charset="UTF-8"></pre><div class="contentsignin"></div></div>）。UTF-8几乎支持世界上所有的字符，这意味着大部分非ASCII字符可以直接在HTML文件中输入并显示，而不需要依赖实体字符。实体字符更多是用来处理那些与HTML语法冲突的字符，或者作为一种万无一失的备用方案。</p></li> <li><p><strong>利用在线工具和参考资料：</strong> 遇到不熟悉的特殊符号，或者需要查找某个字符的实体编码时，不要犹豫去查阅在线资源。W3Schools的HTML实体列表是一个非常好的起点，或者搜索“HTML entity converter”也能找到很多实用的工具，它们可以帮你快速查找和转换字符。我个人就经常把一些生僻的符号丢到这些工具里，看看它对应的实体是什么，省去了很多记忆的麻烦。</p></li> </ol> <p>掌握HTML实体字符的使用，不仅能让你的网页内容显示得更准确、更专业，还能在一定程度上提升网站的安全性，这在日常开发中是不可或缺的基本功。</p>
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