mb_strrpos() Third Argument Is Not Encoding

The third argument of mb_strrpos() was the offset where to start the search in the string. It was often 0, although the 4th argument was the encoding. Since the encoding was more often used, and the offset forgotten, mb_strrpos() used to recognize the encoding when it is used in position 3, and use it. In PHP 8.0, it is not the case anymore.

PHP code

<?php

// Valid in PHP 7.x
echo mb_strrpos('abc', 'a', 'utf8');

// Valid in PHP 8.+
echo mb_strrpos('abc', 'a', 0, 'utf8');
echo mb_strrpos('abc', 'a', encoding: 'utf8');

?>

Before

PHP Deprecated:  mb_strrpos(): Passing the encoding as third parameter is deprecated. Use an explicit zero offset

Deprecated: mb_strrpos(): Passing the encoding as third parameter is deprecated. Use an explicit zero offset
0

After

PHP Fatal error:  Uncaught TypeError: mb_strrpos(): Argument #3 ($offset) must be of type int, string given

Fatal error: Uncaught TypeError: mb_strrpos(): Argument #3 ($offset) must be of type int, string given

PHP version change

This behavior changed in 8.0