function strstr($stack,$needle,$before=FALSE,$case=FALSE) {
		if (!$needle)
			return FALSE;
		preg_match('/^(.*?)'.preg_quote($needle,'/').'/us'.($case?'i':''),
			$stack,$match);
		return isset($match[1])?
			($before?
				$match[1]:
				$this->substr($stack,$this->strlen($match[1]))):
			FALSE;
	}