PHP Manual
Multibyte String Functions
Perform a regular expression search and replace with multibyte support using a callback

mb_ereg_replace_callback

(PHP 5 >= 5.4.1, PHP 7, PHP 8)

mb_ereg_replace_callback — Perform a regular expression search and replace with multibyte support using a callback

Description

mb_ereg_replace_callback(
    string $pattern,
    callable $callback,
    string $string,
    ?string $options = null
): string|false|null

Scans string for matches to pattern, then replaces the matched text with the output of callback function.

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

Parameters

pattern

The regular expression pattern.

Multibyte characters may be used in pattern.

callback

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

You'll often need the callback function for a mb_ereg_replace_callback() in just one place. In this case you can use an anonymous function to declare the callback within the call to mb_ereg_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.

string

The string being checked.

options

The search option. See mb_regex_set_options() for explanation.

Return Values

The resultant string on success, or false on error. If string is not valid for the current encoding, null is returned.

Changelog

Version	Description
8.0.0	`options` is nullable now.
7.1.0	The function checks whether `string` is valid for the current encoding.

Examples

Example #1 mb_ereg_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 mb_ereg_replace_callback(
"(\d{2}/\d{2}/)(\d{4})",
"next_year",
$text);

?>

The above example will output:

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

Example #2 mb_ereg_replace_callback() using anonymous function

<?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";

echo mb_ereg_replace_callback(
"(\d{2}/\d{2}/)(\d{4})",
function ($matches) {
return $matches[1].($matches[2]+1);
},
$text);
?>

Notes

Note:
The internal encoding or the character encoding specified by mb_regex_encoding() will be used as the character encoding for this function.