字符串函数
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htmlspecialchars_decode

(PHP 5 >= 5.1.0)

htmlspecialchars_decode — Convert special HTML entities back to characters

说明

string htmlspecialchars_decode ( string $string [, int $flags = ENT_COMPAT | ENT_HTML401 ] )

This function is the opposite of htmlspecialchars(). It converts special HTML entities back to characters.

The converted entities are: &, " (when ENT_NOQUOTES is not set), ' (when ENT_QUOTES is set), < and >.

参数

string

The string to decode.

flags

A bitmask of one or more of the following flags, which specify how to handle quotes and which document type to use. The default is ENT_COMPAT | ENT_HTML401.

Available flags constants
Constant Name Description
ENT_COMPAT Will convert double-quotes and leave single-quotes alone.
ENT_QUOTES Will convert both double and single quotes.
ENT_NOQUOTES Will leave both double and single quotes unconverted.
ENT_HTML401 Handle code as HTML 4.01.
ENT_XML1 Handle code as XML 1.
ENT_XHTML Handle code as XHTML.
ENT_HTML5 Handle code as HTML 5.

返回值

Returns the decoded string.

更新日志

版本 说明
5.4.0 The constants ENT_HTML401, ENT_XML1, ENT_XHTML and ENT_HTML5 were added.

范例

Example #1 A htmlspecialchars_decode() example

<?php
$str = "<p>this -&gt; &quot;</p>\n";

echo htmlspecialchars_decode($str);

// note that here the quotes aren't converted
echo htmlspecialchars_decode($str, ENT_NOQUOTES);
?>

以上例程会输出：

<p>this -> "</p>
<p>this -> &quot;</p>

参见

字符串函数
在线手册：中文 英文
PHP手册
PHP手册 - N: Convert special HTML entities back to characters

用户评论:

selimx at live dot com (20-Apr-2011 10:35)

this function

<?php
function htmlkarakter($string)
{
   $string = str_replace(array("&lt;", "&gt;", '&amp;', '&#039;', '&quot;','&lt;', '&gt;'), array("<", ">",'&','\'','"','<','>'), htmlspecialchars_decode($string, ENT_NOQUOTES));

       return $string;
  
}
?>

Before
<description>&lt;div class=&quot;google-ad1&quot;&gt;
  &lt;script type=&#039;text/javascript&#039;&gt;
    GA_googleFillSlot(&quot;EW_News_300x250&quot;);
  &lt;/script&gt;

&lt;/div&gt;

after using the function

<div class="google-ad1">
  <script type='text/javascript'>
    GA_googleFillSlot("EW_News_300x250");
  </script>

pinkgothic at gmail dot com (10-Jun-2010 05:24)

Keep in mind that you should never trust user input - particularly for "mixed-bag" input containing a combination of plain text and markup or scripting code.

Why?

Well, consider someone sending '&amp;<script>alert('XSS');</script>' to your PHP script:

<?php
$var = "&amp;<script>alert('XSS');</script>";
$var = (htmlspecialchars_decode($var) == $var) ? htmlspecialchars($var) : $var;
echo $var;
?>

Since '&amp;' decodes into '&', (htmlspecialchars_decode($var) == $var) will be -false-, thus returning $var without that it's escaped. In consequence, the script-tags are untouched, and you've just opened yourself to XSS.

There is, unfortunately, no reliable way to determine whether HTML is escaped or not that does not come with this caveat that I know of. Rather than try and catch the case 'I've already encoded this', you are better off avoiding double-escaping by simply escaping the HTML as close to the actual output as you can muster, e.g. in the view in an MVC development structure.

benharold at mac dot com (27-Jan-2009 12:48)

or of course:

<?php

$var = "Blue & yellow make green.";

$var = (htmlspecialchars_decode($var) == $var) ? htmlspecialchars($var) : $var;
echo $var; // outputs Blue &amp; yellow make green.

// you can do it a bunch of times, it still won't screw you!

$var = (htmlspecialchars_decode($var) == $var) ? htmlspecialchars($var) : $var;
$var = (htmlspecialchars_decode($var) == $var) ? htmlspecialchars($var) : $var;
echo $var; // still outputs Blue &amp; yellow make green.

?>

Put it in a function. Add it to the method of some abstract data class.

benharold at mac dot com (26-Jan-2009 09:30)

If you use `htmlspecialchars()` to change things like the ampersand (&) into it's HTML equivalent (&amp;), you might run into a situation where you mistakenly pass the same string to the function twice, resulting in things appearing on your website like, as I call it, the ampersanded amp; "&amp;". Clearly nobody want's "&amp;" on his or her web page where there is supposed to be just an ampersand. Here's a quick and easy trick to make sure this doesn't happen:

<?php

$var = "This is a string that could be passed to htmlspecialchars multiple times.";

if (htmlspecialchars_decode($var) == $var) {
    $var = htmlspecialchars($var);
}

echo $var;

?>

Now, if your dealing with text that is a mixed bag (has HTML entities and non-HTML entities) you're on your own.

thomas at xci[ignore_this]teit dot commm (28-Mar-2008 11:03)

The example for "htmlspecialchars_decode()" below sadly does not work for all PHP4 versions.

Quote from the PHP manual:
"get_html_translation_table() will return the translation table that is used internally for htmlspecialchars() and htmlentities()."

But it does NOT! At least not for PHP version 4.4.2.
This was already reported in a bug report (http://bugs.php.net/bug.php?id=25927), but it was marked as BOGUS.

Proof:
  Code:
--------------------
<?php
    var_dump(get_html_translation_table(HTML_SPECIALCHARS,ENT_QUOTES));
    var_dump(htmlspecialchars('\'',ENT_QUOTES));
?>
--------------------

  Output:
--------------------
array
  '"' => '&quot;'
  ''' => '&#39;'
  '<' => '&lt;'
  '>' => '&gt;'
  '&' => '&amp;'

'&#039;'
--------------------

This comment now is not to report this bug again (though I really believe it is one), but to complete the example and warn people of this pitfall.

To make sure your htmlspecialchars_decode fake for PHP4 works, you should do something like this:

<?php
    function htmlspecialchars_decode($string,$style=ENT_COMPAT)
    {
        $translation = array_flip(get_html_translation_table(HTML_SPECIALCHARS,$style));
        if($style === ENT_QUOTES){ $translation['&#039;'] = '\''; }
        return strtr($string,$translation);
    }
?>

Br, Thomas

Wout (28-Jul-2007 05:06)

The following replacement for PHP 4 is a little more complete, as the quote_style is taken into account as well:

if (!function_exists("htmlspecialchars_decode")) {
    function htmlspecialchars_decode($string, $quote_style = ENT_COMPAT) {
        return strtr($string, array_flip(get_html_translation_table(HTML_SPECIALCHARS, $quote_style)));
    }
}

(17-Aug-2006 01:49)

This should be the best way to do it.
(Reposted because the other one seems a bit slower and because those who used the code under called it htmlspecialchars_decode_php4)

<?php

if ( !function_exists('htmlspecialchars_decode') )
{
    function htmlspecialchars_decode($text)
    {
        return strtr($text, array_flip(get_html_translation_table(HTML_SPECIALCHARS)));
    }
}

?>

TheSin (09-May-2006 10:51)

Here is how you can get this function in php < 5.1, just make sure this function is before you try and call the function.

if (!function_exists('htmlspecialchars_decode')) {
        function htmlspecialchars_decode($str, $options="") {
                $trans = get_html_translation_table(HTML_SPECIALCHARS, $options);

                $decode = ARRAY();
                foreach ($trans AS $char=>$entity) {
                        $decode[$entity] = $char;
                }

                $str = strtr($str, $decode);

                return $str;
        }
}

se at designlinks dot net (14-Dec-2005 04:43)

The code supplied by or-k at or-k dot com (14-Sep-2005 09:15) is better served using html_entity_decode() for PHP>=4.3.0.
geoffers@gmail (14-Jul-2005 01:38) offers the best htmlspecialchars_decode() for php4 users.

or-k at or-k dot com (14-Sep-2005 10:15)

that works also with &auml; and &quot; and so on.
get_html_translation_table(HTML_ENTITIES) => offers more characters than HTML_SPECIALCHARS

function htmlspecialchars_decode_PHP4($uSTR)
{
 return strtr($uSTR, array_flip(get_html_translation_table(HTML_ENTITIES, ENT_QUOTES)));
}

geoffers@gmail (14-Jul-2005 02:38)

[Update of previous note, having noticed I forgot to put in quote style]

PHP4 Compatible function:

<?php

function htmlspecialchars_decode_php4 ($str, $quote_style = ENT_COMPAT) {
    return strtr($str, array_flip(get_html_translation_table(HTML_SPECIALCHARS, $quote_style)));
}

?>

geoffers at gmail dot com (14-Jul-2005 02:30)

For PHP4 Compatibility:

<?php

function htmlspecialchars_decode_php4 ($str) {
    return strtr($str, array_flip(get_html_translation_table(HTML_SPECIALCHARS)));
}

?>