首页 \ 问答 \ 我们可以使用这种简单的方法而不是使用变量本身(Can we use this simple method instead of using variable itself)

我们可以使用这种简单的方法而不是使用变量本身(Can we use this simple method instead of using variable itself)

我已经标记了许多开发人员使用

$con1 = mysql_connect('localhost', 'username', 'password');
$rv1 = mysql_select_db('db1'); // not added connection

代替

$con1 = mysql_connect('localhost', 'username', 'password');
$rv1 = mysql_select_db('db1', $con1); // added connection

我可以知道这两者之间的区别吗?

实际上这两者都给出了相同的结果


I have marked many of developers using

$con1 = mysql_connect('localhost', 'username', 'password');
$rv1 = mysql_select_db('db1'); // not added connection

Instead

$con1 = mysql_connect('localhost', 'username', 'password');
$rv1 = mysql_select_db('db1', $con1); // added connection

Can I know the difference between this both?

Actually this both are giving same result


原文:https://stackoverflow.com/questions/23243092
更新时间:2020-03-26 12:06

最满意答案

如果您没有传递显式连接参数, mysql_函数将隐式使用使用mysql_connect打开的最后一个连接。 所以,是的,在这种情况下,无论您是否传递参数,结果都是相同的。 如果碰巧使用mysql_connect打开多个连接,您将得到不同的结果。

请注意,隐含地依赖于开放连接是不好的做法,正是因为如果您需要稍后打开更多连接,您的应用程序将会搞砸。 另请注意,mysql_ API已死,切换到mysqli或PDO。


The mysql_ functions will implicitly use the last connection which was opened with mysql_connect, if you do not pass an explicit connection parameter. So, yes, in this case it's the same result whether you pass the parameter or not. You will get different results should you happen to open more than one connection using mysql_connect.

Note that implicitly relying on an open connection is bad practice, precisely because your application will screw up if you need to open more connections sometime later. Also note that the mysql_ API is dead, switch to mysqli or PDO.

2014-04-23

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