public static function indexOf($string, $substring, $offset = null)
	{
		//get the position of this string in the main string
		$position = strpos($string, $substring, $offset);

		//return -1 of the substring was not found
		if( ! is_int($position) )
		{
			//return string position  as -1
			return -1;

		}

		//return actual string position if found
		return $position;
	}