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：
/**
* 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
// 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
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。