public function getConnection($db_host, $db_port, $db_name, $db_user, $db_pass){
		$con_name = $db_host . '_' . $db_name;

		try {
			if (!isset($this->connection[$con_name])) {
				$this->connection[$con_name] = new PDO('mysql:host=' . $db_host . ';port=' . $db_port . ';dbname=' . $db_name . ';charset=utf8', $db_user, $db_pass, array(PDO::ATTR_PERSISTENT => true, PDO::ATTR_TIMEOUT => 5));
				$this->connection[$con_name]->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

				if (debugEnabled()) {
					exit('Failed to connect to DB: ' . $e->getMessage());
				}

				return NULL;

				if (debugEnabled()) {
					exit('Failed to connect to DB: ' . $d->getMessage());
				}

				return NULL;
			}
		}
		catch (PDOException $e) {
			exit('Failed to connect to DB: ' . $e->getMessage());
			return NULL;
		}
		catch (Exception $d) {
			exit('Failed to connect to DB: ' . $d->getMessage());
			return NULL;
		}

		return $db_host . '_'[$con_name];
	}