Description:
------------
The offset parameter of the strrpos function is the offset from the end of the string. The documentation is unclear about this:
 "As of PHP 5.0.0 offset may be specified to begin searching an arbitrary number of characters into the string."
I would expect it to start at $string+$offset, searching backwards.

Reproduce code:
---------------
<?php
	echo "strrpos with offset\n";
	$string='abcdefghijklmnopqrstuvwxyz';
	echo "string: $string\n";
	echo 'strrpos($string, \'n\', 5): '.strrpos($string, 'n', 5)."\n";
	echo 'strrpos($string, \'n\', 15): '.strrpos($string, 'n', 15)."\n";
	echo 'strrpos($string, \'n\', -5): '.strrpos($string, 'n', -5)."\n";
	echo 'strrpos($string, \'n\', -15): '.strrpos($string, 'n', -15)."\n";
?>

Actual result:
--------------
strrpos with offset
string: abcdefghijklmnopqrstuvwxyz
strrpos($string, 'n', 5): 13
strrpos($string, 'n', 15): 
strrpos($string, 'n', -5): 13
strrpos($string, 'n', -15):