mysqli::ping()

(PHP 5, PHP 7)

ping 一个连接，或者如果连接处于断开状态，重新连接

说明

面向对象风格
mysqli::ping(void): bool

过程化风格
mysqli_ping(mysqli$link): bool

检查到服务器的连接是否还正常。在启用mysqli.reconnect选项的前提下，如果连接已经断开， ping 操作会尝试重新建立连接。

Note: mysqlnd 驱动会忽略php.ini中的 mysqli.reconnect 选项，所以它不会自动重连。

客户端建立连接之后，长时间处于闲置状态，可以用此函数来检查服务器是否关闭了这个连接，如有必要，将会自动重新建立到服务器的连接。

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()例程

面向对象风格

<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");
/* 检查连接 */
if ($mysqli->connect_errno) {
    printf("Connect failed: %s\n", $mysqli->connect_error);
    exit();
}
/* 检查连接是否还活跃 */
if ($mysqli->ping()) {
    printf ("Our connection is ok!\n");
} else {
    printf ("Error: %s\n", $mysqli->error);
}
/* 关闭连接 */
$mysqli->close();
?>

过程化风格

<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "world");
/* 检查连接 */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}
/* 检查连接是否还活跃 */
if (mysqli_ping($link)) {
    printf ("Our connection is ok!\n");
} else {
    printf ("Error: %s\n", mysqli_error($link));
}
/* 关闭连接 */
mysqli_close($link);
?>

以上例程会输出：

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 ;))