int substr_compare ( string $main_str , string $str , int $offset [, int $length [, bool $case_insensitivity = false ]] )
substr_compare() compares main_str from position offset with str up to length characters.
Returns < 0 if main_str from position offset is less than str, > 0 if it is greater than str, and 0 if they are equal. If offset is equal to or greater than the length of main_str or length is set and is less than 1, substr_compare() prints a warning and returns FALSE.