PDO MySQL连接关闭-未设置vs空 [英] PDO MySQL Connection close - unset vs null

问题描述

我已经阅读了PDO手册，要关闭连接，您应该使用以下命令:

I've read in PDO manual that to close connection you should use the following:

$connection = null;

但是，有人建议，由于PHP 5.3具有新的GC，因此应使用以下内容:

However, Some people suggested that since PHP 5.3 has a new GC, the following should be used:

unset($connection);

我需要一劳永逸地知道，哪个是首选，还是相同?

I need to know once and for all, which one is preferred, or are they the same?

推荐答案

他们做同样的事情.取消设置$pdo手柄并将其设置为null都会关闭连接.

They do the same thing. Unsetting the $pdo handle and setting it null both close the connection.

您可以自己测试.在一个窗口中运行以下脚本，然后在第二个窗口中打开MySQL客户端，每隔几秒钟运行SHOW PROCESSLIST，以查看连接何时消失.

You can test this for yourself. Run the following script in one window, and in a second window open the MySQL client and run SHOW PROCESSLIST every couple of seconds to see when the connection disappears.

<?php

$pdo = new PDO(..);
sleep(10);
unset($pdo);
echo "pdo unset!\n";
sleep(10);

然后将unset($pdo)更改为$pdo=null;并再次运行测试.

Then change unset($pdo) to $pdo=null; and run the test again.

<?php

$pdo = new PDO(..);
sleep(10);
$pdo = null;
echo "pdo set null!\n";
sleep(10);

在PHP脚本终止之前，多余的sleep()可以让您有一段时间看到连接已断开(无论如何都会断开连接).

The extra sleep() at the end is there to give you a moment to see that the connection has dropped, before the PHP script terminates (which would drop the connection anyway).

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