Description:
------------
strrpos() does not return the proper values when the string contains a null character. 

strpos() works properly.

Reproduce code:
---------------
$test = "Hello";
var_dump(strpos($test, 'e'));
var_dump(strrpos($test, 'e'));
$test = "\x00Hello";
var_dump(strpos($test, 'e'));
var_dump(strrpos($test, 'e'));
$test = "Hello\x00";
var_dump(strpos($test, 'e'));
var_dump(strrpos($test, 'e'));

Expected result:
----------------
int(1)
int(1)
int(2)
int(2)
int(1)
int(1)

Actual result:
--------------
int(1)
int(1)
int(2)
bool(false)
int(1)
int(2)