Reconnectable PDO

reconnecting_pdo.php

<?php
class ReconnectingPDO
{
    protected $dsn, $username, $password, $pdo, $driver_options;
    
    public function __construct($dsn, $username = "", $password = "", $driver_options = array())
    {
        $this->dsn = $dsn;
        $this->username = $username;
        $this->password = $password;
        $this->driver_options = $driver_options;
    }

    public function __call($name, array $arguments)
    {
        try {
            $this->connection()->query("SHOW STATUS;")->execute();
        } catch(\PDOException $e) {
            if($e->getCode() != 'HY000' || !stristr($e->getMessage(), 'server has gone away')) {
                throw $e;
            }

            $this->reconnect();
        }

        return call_user_func_array(array($this->connection(), $name), $arguments);
    }

    protected function connection()
    {
        return $this->pdo instanceof \PDO ? $this->pdo : $this->connect();
    }

    public function connect()
    {
        $this->pdo = new PDO($this->dsn, $this->username, $this->password, (array) $this->driver_options); 
        $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        return $this->pdo;
    }

    public function reconnect()
    {
        $this->pdo = null;
        return $this->connect();
    }
}

In a long-running app, likely the most appropriate thing to do, is don't even attempt to "replay" the query - instead, just throw an exception immediately after reconnecting. Assuming you have an error-handler that can gracefully fail and handle the exception, the current request will fail, but the long-running app itself can continue running and handle the next request.

It's no ideal, but probably only happens if the DB server is down - this at least ensures the long-running app is up and handling requests again as soon as the DB server is back.