public static function indexOf(string $haystack, string $needle, int $offset = 0): int
    {
        $pos = self::strpos($haystack, $needle, $offset);
        return is_int($pos) ? $pos : -1;
    }
public static function indexOf(string $haystack, string $needle, int $offset = 0): int
    {
        $pos = self::strpos($haystack, $needle, $offset);
        return is_int($pos) ? $pos : -1;
    }
public static function indexOf ( string $ haystack , string $ needle , int $ offset = 0 ) : int { $ pos = self :: strpos ( $ haystack , $ needle , $ offset ) ; return is_int ( $ pos ) ? $ pos : - 1 ; }
Index of.

@param string $haystack
@param string $needle
@param int $offset
@return int
Index of .