add function to Logger err()

Logger::err()

public static function err($str)
	{
		
		if ( !strlen($str) ) {
			return false;
		}

		if ( empty(self::$log) ) {
			self::$log = new Logger(LOG_NAME);
		}
		if (self::$log->level < self::ERR) {
			return false;
		}

		$trc = debug_backtrace();
		$s = "[" . date('Y-m-d H:i:s') . "]";
		$s .= "[ERR][PID=" . trim(self::$log->processID) . "]";
		
		$fileList = preg_split('[\/]', $trc[0]['file']);
		$s .= "[file=" . $fileList[count($fileList) - 1] . "]";
		$s .= "[func=" . $trc[0]['function'] . "]";
		$s .= "[line=" . $trc[0]['line'] . "]";
		$s .= "[ip=" . trim(self::$log->ip) . "]";
		$s .= $str;
		self::_write($s);

		return true;
	}