Replace the last occurrence of a string.

str_replace_last.php

<?php
/**
 *  Replace the last occurrence of a string.
 *
 *  @param   string  $search   The string to search for
 *  @param   string  $replace  The string to replace the search string
 *  @param   string  $subject  The string to search and replace
 *  @return  string            The new string
 */
function str_replace_last( $search=null, $replace=null, $subject=null ) {
    return strrev( implode( strrev( $replace ), explode( $search, strrev( $subject ), 2 ) ) );
}