它看起来像错误是在PHP code。

It looks like the error is in the PHP code.

更改以下行： -

发件人：

 $query = mysql_query("SELECT * FROM user WHERE username = '$un' AND password = '$pw'");

到

$query = "SELECT * FROM user WHERE username = '$un' AND password = '$pw'";

您也应该考虑改变prevent SQL注入： -

You should also consider making changes to prevent SQL Injection:-

$query = sprintf("SELECT * FROM user WHERE username = 
    WHERE username='%s' AND password='%s'",
    mysql_real_escape_string($un),
    mysql_real_escape_string($pw));