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preg_replace_callback

(PHP 4 >= 4.0.5, PHP 5)

preg_replace_callback — 执行一个正则表达式搜索并且使用一个回调进行替换

说明

mixed preg_replace_callback ( mixed $pattern , callable $callback , mixed $subject [, int $limit = -1 [, int &$count ]] )

这个函数的行为除了可以指定一个 callback 替代 replacement 进行替换字符串的计算，其他方面等同于 preg_replace() 。

参数

pattern

要搜索的模式，可以使字符串或一个字符串数组。

callback

一个回调函数，在每次需要替换时调用，调用时函数得到的参数是从subject 中匹配到的结果。回调函数返回真正参与替换的字符串。这是该回调函数的签名：

string handler ( array $matches )

你可能经常会需要callback函数而仅用于 preg_replace_callback() 一个地方的调用。在这种情况下，你可以使用匿名函数来定义一个匿名函数作为 preg_replace_callback() 调用时的回调。这样做你可以保留所有调用信息在同一个位置并且不会因为一个不在任何其他地方使用的回调函数名称而污染函数名称空间。

Example #1 preg_replace_callback() 和匿名函数

  <?php
 
 $fp  =  fopen ( "php://stdin" ,  "r" ) or die( "can't read stdin" );
while (! feof ( $fp )) {
     $line  =  fgets ( $fp );
     $line  =  preg_replace_callback (
         '|<p>\s*\w|' ,
        function ( $matches ) {
            return  strtolower ( $matches [ 0 ]);
        },
         $line
     );
    echo  $line ;
}
 fclose ( $fp );
 ?>

subject

要搜索替换的目标字符串或字符串数组。

limit

对于每个模式用于每个 subject 字符串的最大可替换次数。默认是-1（无限制）。

count

如果指定，这个变量将被填充为替换执行的次数。

返回值

如果subject是一个数组， preg_replace_callback() 返回一个数组，其他情况返回字符串。错误发生时返回 NULL 。

如果查找到了匹配，返回替换后的目标字符串（或字符串数组），其他情况subject 将会无变化返回。

更新日志

版本	说明
5.1.0	增加了参数`count`。

范例

Example #2 preg_replace_callback() 示例

  <?php
 // 将文本中的年份增加一年.
 $text  =  "April fools day is 04/01/2002\n" ;
 $text .=  "Last christmas was 12/24/2001\n" ;
 // 回调函数
 function  next_year ( $matches )
{
   // 通常: $matches[0]是完成的匹配
  // $matches[1]是第一个捕获子组的匹配
  // 以此类推
   return  $matches [ 1 ].( $matches [ 2 ]+ 1 );
}
echo  preg_replace_callback (
             "|(\d{2}/\d{2}/)(\d{4})|" ,
             "next_year" ,
             $text );

 ?>

以上例程会输出：

April fools day is 04/01/2003
Last christmas was 12/24/2002

Example #3 preg_replace_callback() 使用递归构造处理BB码的封装

  <?php
$input  =  "plain [indent] deep [indent] deeper [/indent] deep [/indent] plain" ;

function  parseTagsRecursive ( $input )
{
      

	class JWI {


		static function read($filename) {

			if(!file_exists($filename))

				throw new Exception('<b>JWI Error: JSON file <tt>'.$filename.'</tt> not found!</b>');

			$content = join('', file($filename));

			$dir = dirname($filename);


			$content = preg_replace_callback(

				'/{{{\s*"\s*(.+)\s*"\s*}}}/', // >include file< - pattern

				create_function(

					'$matches', // callback parameter

					sprintf(

						'$fn = "%s/".$matches[1];'.

						'return JWI::read($fn);',

						realpath(dirname($filename))

					)

				),

				$content

			);

			return $content;

		}

	}

[#11] henzeberkheij at gmail dot com [2011-11-23 08:23:50]

also note that when you are using this functionality in a class and you need variables in that class, you can use a non static function as callback. array($this, functionName) should be enough to call an function of the class.

Either use create_function if you require the code only once,
use a static class function if no need for accessing variables in that class. or use the array metioned earlier in my post for having access to class variables or other functions!

[#12] webmaster at mp3s dot pl [2011-07-28 00:57:47]

I noticed that 'e' modifier use addslashed on result

<?php function wyczysc_strongi($string) { if(mb_strlen($string,'UTF-8')>60) { return $string; } else { return ''.$string.''; } } $tresc = "fajna dupa's"; $tresc = preg_replace("/(.*?)<\/strong>/ie",'wyczysc_strongi("$1")',$tresc); echo $tresc will give: fajna dupa\'s ?>

solution: $tresc = stripslashes($tresc);
after callback

[#13] aleksander at throw dot pl [2011-01-10 14:59:07]

I needed a simple code to tidy up a string. It simply had to upper-case letters after dot. Simple code to do so:

<?php $string = preg_replace_callback( '|(?:\.)(?:\s*)(\w{1})|Ui', create_function('$matches', 'return ". ".strtoupper($matches[1]);'), ucfirst($string) ); ?>

<?php $string = 'lorem ipsum dolor sit amet, consectetur adipiscing elit. sed ullamcorper diam eu lorem varius nec porta elit iaculis.'; echo preg_replace_callback( '|(?:\.)(?:\s*)(\w{1})|Ui', create_function('$matches', 'return ". ".strtoupper($matches[1]);'), ucfirst($string) ); ?>

Will output: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed ullamcorper diam eu lorem varius nec porta elit iaculis.

<?php $string = 'lorem ipsum dolor sit amet, consectetur adipiscing elit. sed ullamcorper diam eu lorem varius nec porta elit iaculis.'; echo preg_replace_callback( '|(?:\.)(?:\s*)(\w{1})|Ui', create_function('$matches', 'return ". ".strtoupper($matches[1]);'), ucfirst($string) ); ?>

Will output: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed ullamcorper diam eu lorem varius nec porta elit iaculis.

Nothing fancy, but useful :)

[#14] alex dot cs00 at yahoo dot ca [2010-10-06 14:09:14]

Don't use this function to fetch BBCode, as explained. If you have some text that runs over 5000 chars (average), it will run out of its limit and makes you download the PHP page.

According to this, you should instead use something more advanced yet complex. You will need a function called "str_replace_once()" (search for it), one called "countWord()", the famous "after()", "before()", "between()".

str_replace_once does same as str_replace, but only replace first occurence. As for countWord, I guess you know how to count the number of a word occurence. As for after, before and between, this is a function that you may find easily somewhere on the site by a user. Else, you can do it.

The following function is able to do all blocks, supposing and , you might wish things between parents dont get parsed, including [code] if inside of another [code].

<?php function prepareCode($code, $op, $end) { $ix = 0; $iy = 0; $nbr_Op = countWord($op, $code); while($ix < $nbr_Op) { if(in_string($op, before($end, $code), false)) { // The following piece of code replace the default [tag] by [tag:#] $code = str_replace_once($op, substr($op, 0, -1).':'.$ix.']', $code); $iy++; } elseif(in_string($end, before($op, $code), false)) { $iy = $iy-1; $code = str_replace_once($end, substr($end, 0, -1).':'.($ix-1).']', $code); $ix = $ix-2; } $ix++; } while(in_string($end, $code)) { $code = str_replace_once($end, substr($end, 0, -1).':'.($iy-1).']', $code); $iy=$iy-1; } $code = preg_replace('#\\'.substr($end, 0, 1).':-[0-9]\]#i', '', $code); if(in_string(substr($op, 0, -1).':0]', $code) && !in_string(substr($end, 0, -1).':0]', $code)) { $code .= substr($end, 0, -1).":0]"; } return $code; } ?>

$code returns the whole text semi-formated. You only need to use it as :
$code = prepareCode($code="Your text", $op="[tag]" , $end="[/tag]");
Then just replace the parent tags :
str_replace("[tag:0]", "<tag>", $code);
str_replace("[/tag:0]", "</tag>", $code);
So at the end something like :
[

[#15] chris at ocproducts dot com [2010-07-02 07:39:14]

The pcre.backtrack_limit option (added in PHP 5.2) can trigger a NULL return, with no errors. The default pcre.backtrack_limit value is 100000. If you have a match that exceeds about half this limit it triggers a NULL response.
e.g. My limit was at 100000 but 500500 triggered a NULL response. I'm not running unicode but I *guess* PCRE runs in utf-16.

[#16] Anonymous [2010-06-09 12:01:20]

Created this to fetch the link and name of an anchor tag. I use this when cleaning an HTML email to text. Using regex for HTML is not recommended but for this purpose I see no issue with it. This is not designed to work for nested anchors.

A note to keep in mind:
I was primarily concerned with valid HTML so if attributes do no use ' or " to contain the values then this will need to be tweaked.
If you can edit this to work better, please let me know.
<?php function replaceAnchorsWithText($data) { $regex = '/(<a\s*'; // Start of anchor tag $regex .= '(.*?)\s*'; // Any attributes or spaces that may or may not exist $regex .= 'href=[\'"]+?\s*(?P<link>\S+)\s*[\'"]+?'; // Grab the link $regex .= '\s*(.*?)\s*>\s*'; // Any attributes or spaces that may or may not exist before closing tag $regex .= '(?P<name>\S+)'; // Grab the name $regex .= '\s*<\/a>)/i'; // Any number of spaces between the closing anchor tag (case insensitive) if (is_array($data)) { // This is what will replace the link (modify to you liking) $data = "{$data['name']}({$data['link']})"; } return preg_replace_callback($regex, 'replaceAnchorsWithText', $data); } $input = 'Test 1: <a href="http: //php.net1">PHP.NET1</a>. '; $input .= 'Test 2: <A name="test" HREF=\'HTTP: //PHP.NET2\' target="_blank">PHP.NET2</A>. '; $input .= 'Test 3: <a hRef=http: //php.net3>php.net3</a> '; $input .= 'This last line had nothing to do with any of this'; echo replaceAnchorsWithText($input).'<hr/>'; ?>
Will output:
Test 1: PHP.NET1(http: //php.net1).
Test 2: PHP.NET2(HTTP: //PHP.NET2).
Test 3: php.net3 (is still an anchor)
This last line had nothing to do with any of this

[#17] Drake [2010-03-21 17:48:33]

The good version of the class PhpHex2Str
<?php class PhpHex2Str { private $strings; private static function x_hex2str($hex) { $hex = substr($hex[0], 1); $str = ''; for($i=0;$i < strlen($hex);$i+=2) { $str.=chr(hexdec(substr($hex,$i,2))); } return $str; } public function decode($strings = null) { $this->strings = (string) $strings; return preg_replace_callback('#\%[a-zA-Z0-9]{2}#', 'PhpHex2Str::x_hex2str', $this->strings); } } // Exemple $obj = new PhpHex2Str; $strings = $obj->decode($strings); var_dump($strings); ?>

[#18] Drake [2010-03-21 00:05:49]

Decode Hexa to Strings =)
<?php class PhpHex2Str { private $strings; private function x_hex2str($hex) { $hex = substr($hex[0], 1); $str = ''; for($i=0;$i < strlen($hex);$i+=2) { $str.=chr(hexdec(substr($hex,$i,2))); } return $str; } public function decode($strings = null) { $this->strings = (string) $strings; return preg_replace_callback('#\%[a-zA-Z0-9]{2}#', 'x_hex2str', $this->strings); } } // Example $strings = 'a %20 b%0A h %27 h %23'; $obj = new PhpHex2Str; $strings = $obj->decode($strings); var_dump($strings); ?>

[#19] Matt [2009-09-14 09:24:10]

If you're looking to show only the first digit and last four digits of a credit card number (4xxxxxxxxxxxx2331) use something like this:
preg_replace_callback('/((.)(.*))?(.{4})/', create_function('$x', 'return $x[2].str_repeat("x", strlen($x[3])).$x[4];'), '$CCNUMBER')

[#20] ixiter at gmail dot com [2009-07-28 19:06:54]

When you use preg_replace_callback in a class and have the callback function as a private method of that class, you need to set the callback function name like className::CallBack.
self::CallBack does not work and returns an error:
"Cannot call method self::CallBack() or method does not exist"!

<?php class myClass{ public function parsetext($text){ // parses text and sets literals A - C to lower case // this works return preg_replace_callback('|([a-c])|i', 'myClass::preg_tolower', $text); } public function parsefail($text){ // parses text and sets literals A - C to lower case // this fails return preg_replace_callback('|([a-c])|i', 'self::preg_tolower', $text); } private static function preg_tolower($matches){ return strtolower($matches[1]); } } $parser = new myClass; echo $parser->parsetext('ABCDEFGH'); // echoes abcDEFGH echo $parser->parsefail('ABCDEFGH'); // throws the error ?>

[#21] carlos dot ballesteros at softonic dot com [2009-07-02 08:02:24]

A simple function to replace a list of complete words or terms in a string (for PHP 5.3 or above because of the closure):

<?php function replace_words($list, $line, $callback) { return preg_replace_callback( '/(^|[^\\w\\-])(' . implode('|', array_map('preg_quote', $list)) . ')($|[^\\w\\-])/mi', function($v) use ($callback) { return $v[1] . $callback($v[2]) . $v[3]; }, $line ); } ?>

Example of usage:
<?php $list = array('php', 'apache web server'); $str = "php and the apache web server work fine together. php-gtk, for example, won't match. apache web servers shouldn't too."; echo replace_words($list, $str, function($v) { return "{$v}"; }); ?>

[#22] chris AT cmbuckley DOT co DOT uk [2009-06-09 07:44:31]

This function does not support named subpatterns, so you can't do

<?php preg_replace_callback('/(?<char>[a-z])/', 'callback', 'word'); function callback($matches) { var_dump($matches); } ?>

and expect to get $matches['char'] in your function.

[#23] tijn at q-go dot com [2009-01-05 08:48:05]

To access a local variable within a callback, use currying (delayed argument binding). For example
<?php function curry($func, $arity) { return create_function('', " \$args = func_get_args(); if(count(\$args) >= $arity) return call_user_func_array('$func', \$args); \$args = var_export(\$args, 1); return create_function('',' \$a = func_get_args(); \$z = ' . \$args . '; \$a = array_merge(\$z,\$a); return call_user_func_array(\'$func\', \$a); '); "); } function on_match($transformation, $matches) { return $transformation[strtolower($matches[1])]; } $transform = array('a' => 'Well,', 'd'=>'whatever', 'b'=>' '); $callback = curry(on_match, 2); echo preg_replace_callback('/([a-z])/i', $callback($transform), 'Abcd'); echo "\n"; ?>

outputs:

"Well, whatever"

The magic lies in this curry function I found here: http://www.sitepoint.com/forums/showthread.php?threadid=336758

[#24] nicolaspar at gmail dot com [2008-12-19 18:33:17]

To spend more than one parameter can do the following (note the "e" parameter in preg_replace function)
<?php $array = array( 1=>'ONE', 2=>'TWO', 3=>'Three' ); function search(&$array, $str, $foo, $bar){ return ( empty($array[$str]) ? '['.$foo.'-'.$bar.']' : $array[$str] ); } function keys(&$array, $str,$foo,$bar){ return preg_replace('/\[(.*?)\]/e',"search(\$array,$1,\$foo,\$bar)",$str); } $str = "One [1] Two [2] Three [3], Other parameter [22]"; echo keys($array, $str,'Foo','Bar'); ?>
Nice

[#25] nene at triin dot net [2008-05-20 03:14:31]

The first example is bad, because it creates function for every line it processes. When the file has many lines, you could easily run out of memory. The code should be changed so, that create_function() is used outside of loop.

[#26] Sjon at hortensius dot net [2007-06-24 04:56:52]

preg_replace_callback returns NULL when pcre.backtrack_limit is reached; this sometimes occurs faster then you might expect. No error is raised either; so don't forget to check for NULL yourself

[#27] matt at mattsoft dot net [2006-04-26 02:16:12]

it is much better on preformance and better practice to use the preg_replace_callback function instead of preg_replace with the e modifier.

function a($text){return($text);}

// 2.76 seconds to run 50000 times
preg_replace("/\{(.*?)\}/e","a('\\1','\\2','\\3',\$b)",$a);

// 0.97 seconds to run 50000 times
preg_replace_callback("/\{(.*?)\}/s","a",$a);