How to determine whether the connection is available through PDO in php

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

<?phprequire &#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. Execute

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

mysql.server stopShutting down MySQL
.... SUCCESS! 
mysql.server start
Starting MySQL
 SUCCESS!

Execution output:

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

)
sleep 10connect failureArray(
    [0] => Array
        (
            [id] => 3
            [name] => terry
        )

)
sleep 10connect okArray(
    [0] => Array
        (
            [id] => 3
            [name] => terry
        )

)
sleep 10

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

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