PHP preg_replace_callback() function

Author：Eve Cole Update Time：2024-12-28 11:48:01

The preg_replace_callback function performs a regular expression search and replaces it using a callback.

grammar

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

The behavior of this function is equivalent to preg_replace() except that you can specify a callback instead of replacement to calculate the replacement string.

Parameter description:

$pattern: The pattern to search for, which can be a string or an array of strings.

$callback: A callback function that is called every time a replacement is needed. The parameters obtained by the function when called are the results matched from the subject.

$subject: The target string or string array to be searched and replaced.

$limit: Optional, the maximum number of substitutions for each subject string per pattern. The default is -1 (no limit).

$count: Optional, the number of times the replacement is performed.

return value

If subject is an array, preg_replace_callback() returns an array, otherwise it returns a string. Returns NULL when an error occurs.

If a match is found, the replaced target string (or string array) is returned. Otherwise, the subject will be returned unchanged.

Example

Example 1

<?php // Add one year to the year in the text. $text = " April fools day is 04/01/2002 n " ; $text .= " Last christmas was 12/24/2001 n " ; // Callback function function next_year ( $matches ) { // Normally: $matches[0] is the completed match // $matches[1] is the match of the first captured subgroup // and so on return $matches [ 1 ] . ( $matches [ 2 ] + 1 ) ; } echo preg_replace_callback ( " |(d{2}/d{2}/)(d{4})| " , " next_year " , $text ) ; ?>

The execution result is as follows:

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