如果数据库脱机，如何防止MySQLi崩溃PHP脚本

Question

I have the following scenario:

I have a script that conencts to a remote database, and all works good unless the remote database is offline or the server is offline.

If database/server goes offline, the script uses long time to execute, what would be the best way to check if db connection was successfull before executing the SQL?

class remote_db{

    public $db;

    public function __construct(){

        $this->db = new mysqli("127.0.0.1","usr","pw","database");
        $this->db->set_charset("utf8");
    }
}


$remote_db = new remote_db();
if($remote_db){ echo 'hello world';}

Answer 1

There's no reason to check if it's online or not before running a query, since between the time you check, and the time you run the query, it might have gone offline. So simply run the query, and check for error afterwards, as you would normally do:

$r = $db->query('...');
if ($r === false) throw new Exception('error running query');

Also check for errors when you create the connection:

$mysqli = new mysqli('localhost', 'my_user', 'my_password', 'my_db');

if ($mysqli->connect_error) {
    die('Connect Error (' . $mysqli->connect_errno . ') '
            . $mysqli->connect_error);
}

You can also change the timeout property to reduce the waiting time:

$db->options(MYSQLI_OPT_CONNECT_TIMEOUT, 5); // Wait for 5 seconds max