无法辨认的情况

Question

我有这段代码：

mysql_connect('localhost', 'user', 'pass');
            mysql_select_db('db');
    $$checkusername = mysql_query("SELECT `Username` FROM `users` WHERE `EmailAddress` = '".$email."'");
 if(mysql_num_rows($checkusername) == 1)
 {
    echo "<SCRIPT LANGUAGE='JavaScript'>
    window.alert('Sorry, that username is taken. Please go back and try again.')
    </SCRIPT>";
 }
 else
 {
echo 'Username Available';
}

实际上，用户名不可用但仍与“用户名可用”相呼应。我也试过这个但仍然是这样的：

mysql_query("SELECT * FROM `users` WHERE `EmailAddress` = '".$email."'");

我不知道我哪里出错了。

Answer 1

摆脱双美元符号：

   $$checkusername = mysql_query("SELECT `Username` FROM `users` WHERE `EmailAddress` = '".$email."'");

应该是

   $checkusername = mysql_query("SELECT `Username` FROM `users` WHERE `EmailAddress` = '".$email."'");