PDO implements a method to determine whether the connection is available

This article mainly introduces the method of php PDO to determine whether the connection is available. Interested friends can refer to it. I hope it will be helpful to everyone.

mysql_ping() Checks whether the connection to the server is normal. Returns true if a connection to the server is available, false otherwise.

But PDO does not support the mysql_ping() method, so you need to write your own code to simulate the mysql_ping() method to check whether the connection is available.

The code is as follows:

<?php
/**
 * 检查连接是否可用
 * @param Link $dbconn 数据库连接
 * @return Boolean
 */
function pdo_ping($dbconn){
  try{
    $dbconn->getAttribute(PDO::ATTR_SERVER_INFO);
  } catch (PDOException $e) {
    if(strpos($e->getMessage(), &#39;MySQL server has gone away&#39;)!==false){
      return false;
    }
  }
  return true;
}
?>

Code demonstration:

1. Create a test data table

CREATE TABLE `user` (
 `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
 `name` varchar(20) NOT NULL,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

2. Insert test data

insert into user(name) values('fdipzone'),('xfdipzone'),('terry');

mysql> select * from user;
+----+-----------+
| id | name   |
+----+-----------+
| 1 | fdipzone |
| 2 | xfdipzone |
| 3 | terry   |
+----+-----------+

3. Demo file

db.php

##

<?php
// 数据库操作类
class DB{

  // 保存数据库连接
  private static $_instance = null;

  // 连接数据库
  public static function get_conn($config){
    if(isset(self::$_instance) && !empty(self::$_instance)){
      return self::$_instance;
    }

    $dbhost = $config[&#39;host&#39;];
    $dbname = $config[&#39;dbname&#39;];
    $dbuser = $config[&#39;user&#39;];
    $dbpasswd = $config[&#39;password&#39;];
    $pconnect = $config[&#39;pconnect&#39;];
    $charset = $config[&#39;charset&#39;];

    $dsn = "mysql:host=$dbhost;dbname=$dbname;";
    try {
      $h_param = array(
          PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
      );
      if ($charset != &#39;&#39;) {
        $h_param[PDO::MYSQL_ATTR_INIT_COMMAND] = &#39;SET NAMES &#39; . $charset; //設置默認編碼
      }
      if ($pconnect) {
        $h_param[PDO::ATTR_PERSISTENT] = true;
      }
      $conn = new PDO($dsn, $dbuser, $dbpasswd, $h_param);

    } catch (PDOException $e) {
      throw new ErrorException(&#39;Unable to connect to db server. Error:&#39; . $e->getMessage(), 31);
    }

    self::$_instance = $conn;
    return $conn;
  }

  // 执行查询
  public static function query($dbconn, $sqlstr, $condparam){
    $sth = $dbconn->prepare($sqlstr);
    try{
      $sth->execute($condparam);
    } catch (PDOException $e) {
      echo $e->getMessage().PHP_EOL;
    }
    $result = $sth->fetchAll(PDO::FETCH_ASSOC);
    return $result;
  }

  // 重置连接
  public static function reset_connect(){
    self::$_instance = null;
  }

}
?>

test.php

<?php
require &#39;db.php&#39;;

// 数据库设定
$config = array(
  &#39;host&#39; => &#39;localhost&#39;,
  &#39;dbname&#39; => &#39;user&#39;,
  &#39;user&#39; => &#39;root&#39;,
  &#39;password&#39; => &#39;&#39;,
  &#39;pconnect&#39; => 0,
  &#39;charset&#39; => &#39;&#39;
);

// 循环执行
while(true){

  // 创建数据连接
  $dbconn = DB::get_conn($config);

  // 判断连接是否有效
  $status = pdo_ping($dbconn);

  if($status){
    echo &#39;connect ok&#39;.PHP_EOL;
  }else{
    echo &#39;connect failure&#39;.PHP_EOL;

    // 重置连接
    DB::reset_connect();
    $dbconn = DB::get_conn($config);
  }

  // 执行查询
  $sqlstr = &#39;select * from user where id=?&#39;;
  $condparam = array(mt_rand(1,3));
  $data = DB::query($dbconn, $sqlstr, $condparam);
  print_r($data);

  // 延时10秒
  echo &#39;sleep 10&#39;.PHP_EOL.PHP_EOL;
  sleep(10);

}

/**
 * 检查连接是否可用
 * @param Link $dbconn 数据库连接
 * @return Boolean
 */
function pdo_ping($dbconn){
  try{
    $dbconn->getAttribute(PDO::ATTR_SERVER_INFO);
  } catch (PDOException $e) {
    if(strpos($e->getMessage(), &#39;MySQL server has gone away&#39;)!==false){
      return false;
    }
  }
  return true;
}
?>

4. Execution

Execute test.php in php cli mode, and then immediately execute mysql.server stop and mysql.server start to simulate a flash interruption

mysql.server stop
Shutting down MySQL
.... SUCCESS! 
mysql.server start
Starting MySQL
 SUCCESS!

Execution output:

connect ok
Array
(
  [0] => Array
    (
      [id] => 2
      [name] => xfdipzone
    )

)
sleep 10

connect failure
Array
(
  [0] => Array
    (
      [id] => 3
      [name] => terry
    )

)
sleep 10

connect ok
Array
(
  [0] => Array
    (
      [id] => 3
      [name] => terry
    )

)
sleep 10

You can see that after the interruption, pdo_ping() returns false and the connection fails. Then call automatic reconnection to ensure that subsequent queries can continue to be executed.

The above is the entire content of this article, I hope it will be helpful to everyone's study.

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