無法識別的情況

Question

我有這樣的代碼：

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'; 
} 

在實際中，用戶名不可用，但仍然呼應「用戶名可用」。我也試過這個，但還是一樣的：

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

我不知道我要去哪裏錯了。

Answer 1

擺脫雙美元符號：

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

應該

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