使用數據庫驗證電子郵件

Question

我已經創建了一個表單並使用PHP驗證了所有內容，但無法弄清楚如何驗證數據庫中的電子郵件。如果我在數據庫中輸入了用戶名，我希望它顯示一個錯誤。我有connect.php和

只是一個例子 -

這裏就是我如何驗證密碼 -

if(!empty($_POST['password'])) 
{ 
if($_POST['password'] != $_POST['cpass']) 
{ 
    $errors[] = 'The password and confirm password do not match.'; 
} 
else 
{ 
    $p=trim($_POST['password']); 
} 
} 

這裏就是我想要做的事 -

$getusername = "SELECT username FROM users WHERE ($u,$username)"; 
if($getusername) 
{ 
    echo 'Username is already in use.'; 
} 
else 
{ 
    $g=trim($_POST['username']); 

}

這個結果出現在PARSE ERROR中。

Answer 1

// first define the username from the $_POST variable 
// make sure to escape the value to prevent SQL injection 
$username = mysql_real_escape_string(trim($_POST['username'])); 

// select a user with the posted username 
$sql = "SELECT username FROM users WHERE username = '$username' LIMIT 1"; 

// run the query 
$res = mysql_query($sql) or die(mysql_error()); 

// see if there's a result 
if (mysql_num_rows($res) > 0) { 
    echo 'This username is already taken'; 
} else { 
    // .. do stuff 
}