mysqli::ping

mysqli_ping

(PHP 5, PHP 7)

mysqli::ping -- mysqli_ping — Pings a server connection, or tries to reconnect if the connection has gone down

说明

面向对象风格

bool mysqli::ping ( void )

过程化风格

bool mysqli_ping ( mysqli $link )

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.

Note: The php.ini setting mysqli.reconnect is ignored by the mysqlnd driver, so automatic reconnection is never 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.

参数

link

仅以过程化样式：由mysqli_connect() 或 mysqli_init() 返回的链接标识。

返回值

成功时返回 TRUE， 或者在失败时返回 FALSE。

范例

Example #1 mysqli::ping() example

面向对象风格

<?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();
?>

过程化风格

<?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);
?>

以上例程会输出：

Our connection is ok!

User Contributed Notes

root at jusme dot org 22-Sep-2015 07:00
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.
snooops84 at googlemail dot com 13-Feb-2015 05:56
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 ;))
jay at grooveshark dot com 27-Sep-2014 09:07
This does not work with mysqlnd and is marked as wontfix: https://bugs.php.net/bug.php?id=52561