<?php
$foo = "0123456789a123456789b123456789c";
var_dump(strrpos($foo, '7', -5)); // Starts looking backwards five positions
// from the end. Result: int(17)
var_dump(strrpos($foo, '7', 20)); // Starts searching 20 positions into the
// string. Result: int(27)
var_dump(strrpos($foo, '7', 28)); // Result: bool(false)
?>