If you are using a php version < 5.2.0 AND do not really need case insensitive performing, use mb_strpos instead.
mb_strpos is implemented for PHP 4 >= 4.0.6 and PHP 5
(PHP 5 >= 5.2.0)
mb_stripos — Finds position of first occurrence of a string within another, case insensitive
mb_stripos() returns the numeric position of the first occurrence of needle in the haystack string. Unlike mb_strpos(), mb_stripos() is case-insensitive. If needle is not found, it returns FALSE.
The string from which to get the position of the first occurrence of needle
The string to find in haystack
The position in haystack to start searching
Character encoding name to use. If it is omitted, internal character encoding is used.
Return the numeric position of the first occurrence of needle in the haystack string, or FALSE if needle is not found.