This does not work with mysqlnd and is marked as wontfix: https://bugs.php.net/bug.php?id=52561
(PHP 5, PHP 7)
mysqli::ping -- mysqli_ping — Pings a server connection, or tries to reconnect if the connection has gone down
Object oriented style
Procedural style
Checks whether the connection to the server is working. If it has gone down, and global option mysqli.reconnect is enabled an automatic reconnection is attempted.
This function can be used by clients that remain idle for a long while, to check whether the server has closed the connection and reconnect if necessary.
linkProcedural style only: A link identifier returned by mysqli_connect() or mysqli_init()
Returns TRUE on success or FALSE on failure.
Example #1 mysqli::ping() example
Object oriented style
<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");
/* check connection */
if ($mysqli->connect_errno) {
printf("Connect failed: %s\n", $mysqli->connect_error);
exit();
}
/* check if server is alive */
if ($mysqli->ping()) {
printf ("Our connection is ok!\n");
} else {
printf ("Error: %s\n", $mysqli->error);
}
/* close connection */
$mysqli->close();
?>
Procedural style
<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "world");
/* check connection */
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
/* check if server is alive */
if (mysqli_ping($link)) {
printf ("Our connection is ok!\n");
} else {
printf ("Error: %s\n", mysqli_error($link));
}
/* close connection */
mysqli_close($link);
?>
The above examples will output:
Our connection is ok!
This does not work with mysqlnd and is marked as wontfix: https://bugs.php.net/bug.php?id=52561
As jay at grooveshark dot com very helpfully pointed out, the mysqlnd driver which is becoming pretty standard does not obey reconnect commands. If you have a DB wrapper class (which hopefully you do) you can implement your own version of ping() such as:
<?php
class db extends mysqli
{
private $db_host;
private $db_user;
private $db_pass;
private $db_name;
private $persistent;
public function __construct($db_host, $db_user, $db_pass, $db_name, $persistent = true)
{
$this->db_host = $db_host;
$this->db_user = $db_user;
$this->db_pass = $db_pass;
$this->db_name = $db_name;
$this->persistent = $persistent;
parent::init();
parent::options(MYSQLI_OPT_CONNECT_TIMEOUT, 1);
@parent::real_connect(($this->persistent ? 'p:' : '') . $this->db_host, $this->db_user, $this->db_pass, $this->db_name);
if ($this->connect_errno)
die("All DB servers down!\n");
}
public function ping()
{
@parent::query('SELECT LAST_INSERT_ID()');
if ($this->errno == 2006)
$this->__construct($this->db_host, $this->db_user, $this->db_pass, $this->db_name, $this->persistent);
}
...
}
$db = new db(DB_HOST, DB_USER, DB_PASS, DB_NAME);
// Some code that potentially takes a really long time to execute goes here
// Ping for safety to try to gracefully reconnect
$db->ping();
// Now we should be able to run queries again
$db->query('SELECT LAST_INSERT_ID()');
?>
If you wanted you could even put "$this->ping();" at the top of db::query() to avoid any explicit reconnection calls but I wouldn't recommend it due to the (slight) overhead of running the cheap "SELECT LAST_INSERT_ID()" query every time prior to running your real intended query. There are probably even cheaper queries to run in favor of "SELECT LAST_INSERT_ID()" but it was the first that came to mind and is cheap enough for most purposes since you shouldn't be calling ping() a whole bunch anyway.
The behaviour about the option mysqli.reconnect is default set to Off at Debian PHP Packages. So i would recommend to update the first line description about the recommendation at the option mysqli.reconnect. (practice note ;))