PHP mysql_connect 不返回 boolean 值

Question

我有以下 PHP 代码:

$con = mysql_connect("localhost","name","pass") or die(mysql_error());

$db = "db";

mysql_select_db($db,$con);

根据我的经验，$con 应该是 true 或 false。当我 echo $con 我得到:

Resource id #25

如果我执行以下代码，则 echo 永远不会触发(如上述语句后预期的那样):

if($con) { echo "it worked"; }

当我针对此连接运行查询时，一切都按预期进行。这个 $con 不会为真或为假有什么原因吗？

我做错了什么？

谢谢

Answer 1

检查 mysql_connect返回值:

Returns a MySQL link identifier on success or FALSE on failure.

检查连接:

if($con !== false) { echo "it worked"; }

或在出现错误时退出:

if (!$con) {
    die('Could not connect: ' . mysql_error());
}

不过有个建议，最好使用 MySQLi或 PDO_MySQL而不是 mysql_connect，因为它很快就会被弃用:

Warning

This extension is deprecated as of PHP 5.5.0, and will be removed in the future. Instead, the MySQLi or PDO_MySQL extension should be used. See also MySQL: choosing an API guide and related FAQ for more information. Alternatives to this function include:

mysqli_connect()

PDO::__construct()