如何检查PHP是否已连接到数据库?

问题描述：

基本上在伪代码中，我正在寻找类似的东西

Basically in pseudo code I'm looking for something like

if (connected_to_any_database()) {
    // do nothing
}
else {
    mysql_connect(...)
}

我该如何实现

connected_to_any_database()

答

您是否尝试过 mysql_ping() ?

Have you tried mysql_ping()?

检查与服务器的连接是否正常.如果出现故障，则尝试自动重新连接.

Checks whether or not the connection to the server is working. If it has gone down, an automatic reconnection is attempted.

或者，第二种(不太可靠)的方法是:

Alternatively, a second (less reliable) approach would be:

$link = mysql_connect('localhost','username','password');
//(...)
if($link == false){
    //try to reconnect
}

更新:从PHP 5.5开始，使用 mysqli_ping() .

Update: From PHP 5.5 onwards, use mysqli_ping() instead.