preg_replace_callback

(PHP 4 >= 4.0.5, PHP 5)

preg_replace_callbackEsegue ricerche e sostituzioni con espressioni regolari usando il callback

Descrizione

mixed preg_replace_callback ( mixed $espressione_regolare , callback $callback , mixed $testo [, int $limite ] )

Fondamentalmente questa funzione si comporta come preg_replace(), eccetto che per la presenza del callback. Con quest'ultimo parametro si indica una funzione da richiamare a cui verrà passata una matrice con i testi riconosciuti in testo. La funzione di callback dovrebbe restituire la stringa da sostituire.

Example #1 Esempio dell'uso di preg_replace_callback()

<?php 
// questo test è stato usato nel 2002
// lo si vuole avere aggiornato per il 2003
$text "April fools day is 04/01/2002\n"
$text.= "Last christmas was 12/24/2001\n"
// la funzione di callback
function next_year($matches

// come solito: $matches[0] è il testo riconosciuto completo
// $matches[1] la parte riconosciuta per il primo criterio
// racchiuso in '(...)' e così via
return $matches[1].($matches[2]+1); 
}
echo 
preg_replace_callback(
     
"|(\d{2}/\d{2}/)(\d{4})|",
     
"next_year",
     
$text);
// il risultato sarà:
// April fools day is 04/01/2003
// Last christmas was 12/24/2002
?>

Spesso si ha la necessità di richiamare la funzione callback soltanto in un unico posto. In questo caso si può utilizzare create_function() per dichiarare una funzione anonima come callback per preg_replace_callback().In questo modo si hanno tutte le informazioni per la chiamata in un unico posto e non si disperde con funzioni di callback non utilizzate altrove.

Example #2 preg_replace_callback() e create_function()

<?php
/* Un filtro da linea di comando stile Unix che converte
 * la maiuscole poste all'inizio delle parole in minuscolo */
$fp fopen("php://stdin""r") or die("can't read stdin");
while (!
feof($fp)) {
      
$line fgets($fp);
      
$line preg_replace_callback(
             
'|<p>\s*\w|',
             
create_function(
                  
// l'apice singolo è essenziale qui, 
                  // o in alternativa occorre usare la sequenza di escape \$ 
                  // per tutte le occorrenze di $ 
                 
'$matches',
                 
'return strtolower($matches[0]);' 
                 
), 
               
$line 
      
);
      echo 
$line
}
fclose($fp);
?>

Vedere anche preg_replace() create_function(), e informazioni sul tipo callback.

add a note add a note

User Contributed Notes 26 notes

up
12
Richard
1 year ago
The easiest way to pass more than one parameters to the callback function is with the 'use' keyword.

[This is better than using global, because it works even when we are already inside a function.]

In this example, the callback function is an anonymous function, which takes one argument, $match, supplied by preg_replace_callback().  The extra
"use ($ten)" puts the $ten variable into scope for the function.

<?php
$string
= "Some numbers: one: 1; two: 2; three: 3 end";
$ten = 10;
$newstring = preg_replace_callback(
   
'/(\\d+)/',
    function(
$match) use ($ten) { return (($match[0] + $ten)); },
   
$string
   
);
echo
$newstring;
#prints "Some numbers: one: 11; two: 12; three: 13 end";
?>
up
5
development at HashNotAdam dot com
2 years ago
From PHP 5.3 you can use an anonymous function to pass local variables into the callback.

<?php

public function replace_variables( $subject, $otherVars ) {
   
$linkPatterns = array(
       
'/(<a .*)href=(")([^"]*)"([^>]*)>/U',
       
"/(<a .*)href=(')([^']*)'([^>]*)>/U"
   
);

   
$callback = function( $matches ) use ( $otherVars ) {
       
$this->replace_callback($matches, $otherVars);
    };

    return
preg_replace_callback($this->patterns, $callback, $subject);
}

public function
replace_callback($matches, $otherVars) {
    return
$matches[1] . $otherVars['myVar'];
}
?>
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10
Yuri
1 year ago
If you want to call non-static function inside your class, you can do something like this.

For PHP 5.2 use second argument like array($this, 'replace'):
<?php
class test_preg_callback{

  private function
process($text){
   
$reg = "/\{([0-9a-zA-Z\- ]+)\:([0-9a-zA-Z\- ]+):?\}/";
    return
preg_replace_callback($reg, array($this, 'replace'), $text);
  }
 
  private function
replace($matches){
    if (
method_exists($this, $matches[1])){
      return @
$this->$matches[1]($matches[2]);    
    }
  } 
}
?>

For PHP 5.3 use second argument like "self::replace":
<?php
class test_preg_callback{

  private function
process($text){
   
$reg = "/\{([0-9a-zA-Z\- ]+)\:([0-9a-zA-Z\- ]+):?\}/";
    return
preg_replace_callback($reg, "self::replace", $text);
  }
 
  private function
replace($matches){
    if (
method_exists($this, $matches[1])){
      return @
$this->$matches[1]($matches[2]);    
    }
  } 
}
?>
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3
nene at triin dot net
6 years ago
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.
up
3
matt at languesvivantes dot com
2 years ago
Actually, this only works from php 5.4, see the changelog on http://php.net/manual/en/functions.anonymous.php
up
1
chris at ocproducts dot com
4 years ago
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.
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1
alex dot cs00 at yahoo dot ca
3 years ago
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 [code] and [/code], 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 :
[
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1
nicolaspar at gmail dot com
5 years ago
To spend more than one parameter can do the following (note the "e" parameter in preg_replace function)
<?
$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
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0
ktretyakgm at gmail dot com
1 month ago
I think now I have written a class for full parsing, in particular, bbcode. Parsing is carried out by using preg_replace_callback ().
This class allows you to break apart complex nested structures code.

<?php
/**
* @author Костя Третяк
*/
class Parse {
   
    private
       
$patterns
       
,$substitutions
       
,$pattern
       
,$substitution
   
;
   
   
/**
     * @param mix $str
     * @param string $pattern
     * @param string $substitution
     * @return string
     */
   
protected function replace_recursive($str, $pattern = null, $substitution = null)
    {
        if (
is_array($str))
        {
            unset(
$str[0]);
           
           
$tmp = $this->substitution;
           
            foreach(
$str as $key => $match)
            {
               
$tmp = str_replace('$'.$key, $match, $tmp);
            }
           
           
$str = $tmp;
           
            if ( !empty(
$this->patterns))
            {
               
$obj = new Parse;
               
$str = $obj->next_level($str, $this->patterns, $this->substitutions);
            }
        }
        else
        {
           
$this->pattern = $pattern ?: $this->pattern;
           
$this->substitution = $substitution ?: $this->substitution;
        }
       
        return
preg_replace_callback($this->pattern, array($this, 'replace_recursive'), $str);
    }
   
   
/**
     * @param string $str
     * @param mix $patterns
     * @param mix $substitutions
     * @return string
     */
   
public function next_level($str, $patterns, $substitutions)
    {
       
$this->compare_params($patterns, $substitutions);
       
$this->patterns = $patterns;
       
$this->substitutions = $substitutions;
        return
$this->replace_recursive($str, array_shift($this->patterns), array_shift($this->substitutions));
    }
   
   
/**
     * @param mix $patterns
     * @param mix $substitutions
     * @throws Exception
     */
   
protected function compare_params( & $patterns, & $substitutions)
    {
       
$patterns = (array) $patterns;
       
$substitutions = (array) $substitutions;
       
        if (
count($patterns) != count($substitutions))
        {
            throw new
Exception('The number of elements in the $substitutions array must equal the number of elements in the $patterns array');
        }
    }
   
   
/**
     * @param string $str
     * @param mix $patterns
     * @param mix $substitutions
     * @return string
     */
   
public function replace_tags($str, $patterns, $substitutions)
    {
       
$this->compare_params($patterns, $substitutions);
       
        foreach(
$patterns as $key => $pattern)
        {
           
$str = $this->next_level($str, $pattern, $substitutions[$key]);
        }
       
        return
$str;
    }
}
?>
Examples of use can be viewed on https://gist.github.com/KostyaTretyak/4a9dc3490db73234f956

(Preview my comment http://php.net/manual/en/function.preg-replace-callback.php#115326 can be removed, as it is the best code)
up
0
Matt
4 years ago
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')
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0
ixiter at gmail dot com
5 years ago
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
?>
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0
carlos dot ballesteros at softonic dot com
5 years ago
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
"<strong>{$v}</strong>";
});
?>
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0
chris AT cmbuckley DOT co DOT uk
5 years ago
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 $matches['char'] in your function.
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0
tijn at q-go dot com
5 years ago
To access a local variable within a callback, use currying (delayed argument binding). For example
<?php
function curry($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
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-1
kkatpki
1 year ago
Note that, as of PHP 5.3, it seems that named subpatterns are now included in the matches array by their named key as well as their numerical key.

To build off of Chris' previous example, as of PHP 5.3, you *can* 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. * BUT ONLY AS OF PHP 5.3 *

Please be mindful of this if you intend to support PHP 5.2.
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-1
Florian Arndt
2 years ago
This small class allows PHP users to read JSON files with include statements in them. For instance the include {{{ "relative/to/including.json" }}} is replaced by the content of the json file located at "relative/to/including.json".

<?php
   
/**
     * Handles JSON files with includes
     * Purpose: handle bigger JSON files by featuring "includes"
     *
     * @author Florian Arndt
     */
   
class JWI {
       
/**
         * Parses a JSON file and returns its contents
         * @param String $filename
         */
       
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);
           
/**
             * replace
             *   include statements
             * with
             *   content of the file to include
             * recursively
             */
           
$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
$content;
        }
    }
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-1
henzeberkheij at gmail dot com
2 years ago
also note that when you are using this functionality in a class and you need variables in that class, you can use a non static function as callback. array($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!
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-1
aleksander at throw dot pl
3 years ago
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 :)
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-1
Drake
4 years ago
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);
?>
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-1
Drake
4 years ago
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);
?>
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-1
Sjon at hortensius dot net
7 years ago
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
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-2
Underdog
6 months ago
For the callback I advise only to use a permanent or anonymous function.

Depending on the usage you may encounter memory issues when using create_function for the callback possibly due to attempts at being compatible with PHP 5.2 or prior. Some servers  refuse to update their PHP  for whatever reason.

Please peruse the create_function documentation for more details regarding its memory usage.

Regards.
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matt at mattsoft dot net
8 years ago
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);
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-2
T-Soloveychik at ya dot ru
1 year ago
Text lines numeration:
<?PHP
// Multieline text:
   
$Text = "
Some
Multieline
text
for
numeration"
;

// For count:
   
$GLOBALS["LineNUMBER"] = 1;

// Replace linestart on number:
   
PRINT preg_replace_callback("/^/m",function ()
        {
            return
$GLOBALS["LineNUMBER"]++."  ";
        },
       
$Text);

?>

1
2 Some
3 Multieline
4 text
5 for
6 numeration
up
-1
webmaster at mp3s dot pl
3 years ago
I noticed that 'e' modifier use addslashed on result

<?
function wyczysc_strongi($string) {
    if(mb_strlen($string,'UTF-8')>60) {
        return $string;
    } else {
        return '<strong>'.$string.'</strong>';
    }
}

$tresc = "<strong>fajna dupa's</strong>";

$tresc = preg_replace("/<strong>(.*?)<\/strong>/ie",'wyczysc_strongi("$1")',$tresc);

echo $tresc will give: <strong>fajna dupa\'s</strong>
?>

solution: $tresc = stripslashes($tresc);
after callback
up
-1
Anonymous
4 years ago
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
/**
* Replaces anchor tags with text
* - Will search string and replace all anchor tags with text (case insensitive)
*
* How it works:
* - Searches string for an anchor tag, checks to make sure it matches the criteria
*         Anchor search criteria:
*             - 1 - <a (must have the start of the anchor tag )
*             - 2 - Can have any number of spaces or other attributes before and after the href attribute
*             - 3 - Must close the anchor tag
*
* - Once the check has passed it will then replace the anchor tag with the string replacement
* - The string replacement can be customized
*
* Know issue:
* - This will not work for anchors that do not use a ' or " to contain the attributes.
*         (i.e.- <a href=http: //php.net>PHP.net</a> will not be replaced)
*/
function replaceAnchorsWithText($data) {
   
/**
     * Had to modify $regex so it could post to the site... so I broke it into 6 parts.
     */
   
$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>.<br />';
$input .= 'Test 2: <A name="test" HREF=\'HTTP: //PHP.NET2\' target="_blank">PHP.NET2</A>.<BR />';
$input .= 'Test 3: <a hRef=http: //php.net3>php.net3</a><br />';
$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
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