The mb_ereg_replace_callback() function is an inbuilt function in PHP that is used to replace a regular expression match in a string using the callback function.
Syntax:
mb_ereg_replace_callback( $pattern, $callback,$string,$options): string|false|null
Parameters: The function accepts four parameters that are described below.
- $pattern: A pattern is a regular expression pattern that is used for replacing a string. It must be a valid regular expression pattern.
- $callback: Â A callback function is to be called for each match. The function should accept one parameter (an array containing the match information) and return the replacement string.
- $string: The input string to search in.
- $options: This is an optional parameter. Possible values for this parameter are: ‘m’ for multiline, ‘s’ for single line, and ‘r’ using Unicode rules when matching.
Return values: This function is the input string with all matches of the pattern replaced by the result of the callback function, as a string when it is true, & when it is false then it will give an error. The null will be returned when the string is invalid for the current encoding.
Example 1: The following program demonstrates the mb_ereg_replace_callback() function.
PHP
<?php     $string = "I love cats and dogs"; $pattern = "[a-z]";   $callback = function ($match) {     return mb_strtoupper($match[0]); };   $replaced_string = mb_ereg_replace_callback($pattern, $callback, $string); echo "The string '$string' with matches replaced is '$replaced_string'.";   ?> |
The string 'I love cats and dogs' with matches replaced is 'I LOVE CATS AND DOGS'.
Example 2: The following program demonstrates the mb_ereg_replace_callback() function.
PHP
<?php     $string = "Hello world"; $pattern = "[w]"; $replaced_string = mb_ereg_replace_callback(     $pattern,     function ($matches) {         $first_letter = $matches[0];         if (mb_strtolower($first_letter) == "w") {             return mb_strtoupper($first_letter);         } else {             return $first_letter;         }     },     $string); echo "The string '$string' with matches replaced is '     $replaced_string'."; ?> |
Output:
The string 'Hello world' with matches replaced is 'Hello World'.
Reference: https://www.php.net/manual/en/function.mb-ereg-replace-callback.php
