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HomeBackend DevelopmentPHP TutorialPHP converts predefined characters into html entity function htmlspecialchars()

实例

把预定义的字符 "" (大于)转换为 HTML 实体:

<?php
$str = "This is some <b>bold</b> text.";
echo htmlspecialchars($str);
?>

上面代码的 HTML 输出如下(查看源代码):

<!DOCTYPE html>
<html>
<body>
This is some <b>bold</b> text.
</body>
</html>

上面代码的浏览器输出如下:

This is some <b>bold</b> text.

定义和用法

htmlspecialchars() 函数把一些预定义的字符转换为 HTML 实体。

预定义的字符是:

& (和号)成为 &

" (双引号)成为 "

' (单引号)成为 '

提示:要把特殊的 HTML 实体转换回字符,请使用 htmlspecialchars_decode() 函数。

语法

htmlspecialchars(string,flags,character-set,double_encode)
参数 描述
string 必需。规定要转换的字符串
flags 可选。规定如何处理引号、无效的编码以及使用哪种文档类型。

可用的引号类型:

  • ENT_COMPAT - 默认。仅编码双引号。

  • ENT_QUOTES - 编码双引号和单引号。

  • ENT_NOQUOTES - 不编码任何引号。

无效的编码:

  • ENT_IGNORE - 忽略无效的编码,而不是让函数返回一个空的字符串。应尽量避免,因为这可能对安全性有影响。

  • ENT_SUBSTITUTE - 把无效的编码替代成一个指定的带有 Unicode 替代字符 U+FFFD(UTF-8)或者 FFFD; 的字符,而不是返回一个空的字符串。

  • ENT_DISALLOWED - 把指定文档类型中的无效代码点替代成 Unicode 替代字符 U+FFFD(UTF-8)或者 FFFD;。

规定使用的文档类型的附加 flags:

ENT_HTML401 - 默认。作为 HTML 4.01 处理代码。

ENT_HTML5 - 作为 HTML 5 处理代码。

ENT_XML1 - 作为 XML 1 处理代码。

ENT_XHTML - 作为 XHTML 处理代码。

character-set 可选。一个规定了要使用的字符集的字符串。

允许的值:

  • UTF-8 - 默认。ASCII 兼容多字节的 8 位 Unicode

  • ISO-8859-1 - 西欧

  • ISO-8859-15 - 西欧(加入欧元符号 + ISO-8859-1 中丢失的法语和芬兰语字母)

  • cp866 - DOS 专用 Cyrillic 字符集

  • cp1251 - Windows 专用 Cyrillic 字符集

  • cp1252 - Windows 专用西欧字符集

  • KOI8-R - 俄语

  • BIG5 - 繁体中文,主要在台湾使用

  • GB2312 - 简体中文,国家标准字符集

  • BIG5-HKSCS - 带香港扩展的 Big5

  • Shift_JIS - 日语

  • EUC-JP - 日语

  • MacRoman - Mac 操作系统使用的字符集

注释:在 PHP 5.4 之前的版本,无法被识别的字符集将被忽略并由 ISO-8859-1 替代。自 PHP 5.4 起,无法被识别的字符集将被忽略并由 UTF-8 替代。

double_encode 可选。一个规定了是否编码已存在的 HTML 实体的布尔值。
  • TRUE - 默认。将对每个实体进行转换。

  • FALSE - 不会对已存在的 HTML 实体进行编码。

技术细节

返回值: 返回已转换的字符串。

如果 string 包含无效的编码,则返回一个空的字符串,除非设置了 ENT_IGNORE 或者 ENT_SUBSTITUTE 标志。
PHP 版本: 4+
更新日志 在 PHP 5 中,character-set 参数的默认值改为 UTF-8。

在 PHP 5.4 中,新增了:ENT_SUBSTITUTE、ENT_DISALLOWED、ENT_HTML401、ENT_HTML5、ENT_XML1 和 ENT_XHTML。

在 PHP 5.3 中,新增了 ENT_IGNORE。

在 PHP 5.2.3 中,新增了 double_encode 参数。

在 PHP 4.1 中,新增了 character-set 参数。

更多实例

实例 1

把一些预定义的字符转换为 HTML 实体:

<?php
$str = "Jane & &#39;Tarzan&#39;";
echo htmlspecialchars($str, ENT_COMPAT); // 默认,仅编码双引号
echo "<br>";echo htmlspecialchars($str, ENT_QUOTES); // 编码双引号和单引号
echo "<br>";echo htmlspecialchars($str, ENT_NOQUOTES); // 不编码任何引号
?>

上面代码的 HTML 输出如下(查看源代码):

<!DOCTYPE html>
<html>
<body>
Jane & &#39;Tarzan&#39;<br>Jane & &#39;Tarzan&#39;<br>Jane & &#39;Tarzan&#39;
</body>
</html>

上面代码的浏览器输出如下:

Jane & &#39;Tarzan&#39;
Jane & &#39;Tarzan&#39;
Jane & &#39;Tarzan&#39;

实例 2

把双引号转换为 HTML 实体:

<?php
$str = &#39;I love "PHP".&#39;;
echo htmlspecialchars($str, ENT_QUOTES); // 编码双引号和单引号
?>;

上面代码的 HTML 输出如下(查看源代码):

<!DOCTYPE html>
<html>
<body>
I love "PHP".
</body>
</html>

上面代码的浏览器输出如下:

I love "PHP".

htmlspecialchars_decode() 函数把一些预定义的 HTML 实体转换为字符。

会被解析成

<!DOCTYPE html>
<html>
<body>
This is some <b>bold</b> text.
</body>
</html>

用户商品详情的输出。

<p>
    {sh:$info.intro|htmlspecialchars_decode}
</p>

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