php PDO判断连接是否可用的方法

mysql_ping() 检查到服务器的连接是否正常。如果到服务器的连接可用，则返回true，否则返回false。

但PDO不支持mysql_ping()方法，因此需要自己编写代码模拟mysql_ping()方法，检查连接是否可用。

代码如下：

<?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(), "MySQL server has gone away")!==false){
            return false;
        }
    }
    return true;
}
?>

代码演示：

1.创建测试数据表

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.插入测试数据

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

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

3.演示文件

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["host"];
        $dbname = $config["dbname"];
        $dbuser = $config["user"];
        $dbpasswd = $config["password"];
        $pconnect = $config["pconnect"];
        $charset = $config["charset"];

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

        } catch (PDOException $e) {
            throw new ErrorException("Unable to connect to db server. Error:" . $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 "db.php";

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

// 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 "connect ok".PHP_EOL;
    }else{
        echo "connect failure".PHP_EOL;

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

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

    // 延时10秒
    echo "sleep 10".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(), "MySQL server has gone away")!==false){
            return false;
        }
    }
    return true;
}
?>

4.执行

在php cli模式下执行test.php，然后马上执行mysql.server stop 与 mysql.server start 模拟闪断

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

执行输出：

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

可以看到闪断后，pdo_ping()返回false，连接失败，然后调用自动重连，保证后面的查询能继续执行。