preg_replace_callback

(PHP 4 >= 4.0.5, PHP 5, PHP 7, PHP 8)

preg_replace_callbackPerform a regular expression search and replace using a callback

Description

preg_replace_callback(
    string|array $pattern,
    callable $callback,
    string|array $subject,
    int $limit = -1,
    int &$count = null,
    int $flags = 0
): string|array|null

The behavior of this function is almost identical to preg_replace(), except for the fact that instead of replacement parameter, one should specify a callback.

Parameters

pattern

The pattern to search for. It can be either a string or an array with strings.

callback

A callback that will be called and passed an array of matched elements in the subject string. The callback should return the replacement string. This is the callback signature:

handler(array $matches): string

You'll often need the callback function for a preg_replace_callback() in just one place. In this case you can use an anonymous function to declare the callback within the call to preg_replace_callback(). By doing it this way you have all information for the call in one place and do not clutter the function namespace with a callback function's name not used anywhere else.

Example #1 preg_replace_callback() and anonymous function

<?php
/* a unix-style command line filter to convert uppercase
 * letters at the beginning of paragraphs to lowercase */
$fp fopen("php://stdin""r") or die("can't read stdin");
while (!
feof($fp)) {
    
$line fgets($fp);
    
$line preg_replace_callback(
        
'|<p>\s*\w|',
        function (
$matches) {
            return 
strtolower($matches[0]);
        },
        
$line
    
);
    echo 
$line;
}
fclose($fp);
?>

subject

The string or an array with strings to search and replace.

limit

The maximum possible replacements for each pattern in each subject string. Defaults to -1 (no limit).

count

If specified, this variable will be filled with the number of replacements done.

flags

flags can be a combination of the PREG_OFFSET_CAPTURE and PREG_UNMATCHED_AS_NULL flags, which influence the format of the matches array. See the description in preg_match() for more details.

Return Values

preg_replace_callback() returns an array if the subject parameter is an array, or a string otherwise. On errors the return value is null

If matches are found, the new subject will be returned, otherwise subject will be returned unchanged.

Errors/Exceptions

If the regex pattern passed does not compile to a valid regex, an E_WARNING is emitted.

Changelog

Version Description
7.4.0 The flags parameter was added.

Examples

Example #2 preg_replace_callback() example

<?php
// this text was used in 2002
// we want to get this up to date for 2003
$text "April fools day is 04/01/2002\n";
$text.= "Last christmas was 12/24/2001\n";
// the callback function
function next_year($matches)
{
  
// as usual: $matches[0] is the complete match
  // $matches[1] the match for the first subpattern
  // enclosed in '(...)' and so on
  
return $matches[1].($matches[2]+1);
}
echo 
preg_replace_callback(
            
"|(\d/\d/)(\d)|",
            
"next_year",
            
$text);

?>

The above example will output:

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

Example #3 preg_replace_callback() using recursive structure to handle encapsulated BB code

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

function 
parseTagsRecursive($input)
{

    
$regex '#\[indent]((?:[^[]|\[(?!/?indent])|(?R))+)\[/indent]#';

    if (
is_array($input)) {
        
$input '<div style="margin-left: 10px">'.$input[1].'</div>';
    }

    return 
preg_replace_callback($regex'parseTagsRecursive'$input);
}

$output parseTagsRecursive($input);

echo 
$output;
?>

See Also

Here you can write a comment


Please enter at least 10 characters.
Loading... Please wait.
* Pflichtangabe
There are no comments available yet.

PHP cURL Tutorial: Using cURL to Make HTTP Requests

cURL is a powerful PHP extension that allows you to communicate with different servers using various protocols, including HTTP, HTTPS, FTP, and more. ...

TheMax

Autor : TheMax
Category: PHP-Tutorials

Midjourney Tutorial - Instructions for beginners

There is an informative video about Midjourney, the tool for creating digital images using artificial intelligence, entitled "Midjourney tutorial in German - instructions for beginners" ...

Mike94

Autor : Mike94
Category: KI Tutorials

Basics of views in MySQL

Views in a MySQL database offer the option of creating a virtual table based on the result of an SQL query. This virtual table can be queried like a normal table without changing the underlying data. ...

admin

Autor : admin
Category: mySQL-Tutorials

Publish a tutorial

Share your knowledge with other developers worldwide

Share your knowledge with other developers worldwide

You are a professional in your field and want to share your knowledge, then sign up now and share it with our PHP community

learn more

Publish a tutorial