提交表單時的PHP驗證錯誤

Question

以下代碼無法正常工作，當單擊表單的提交按鈕時，如果沒有輸入任何數據，它將進入blog.php，而不是在表單上方顯示錯誤？

<?php 

session_start();

include_once('connection.php');



if (isset($_SESSION['logged_in'])){
    //display index
} else {
    if (isset($_POST['username'], $_POST['password'])) {
        $username = $_POST['username'];
        $password = $_POST['password'];

        if (empty($username) or empty($password)) {
            $error = 'All fields are required!';
        }
    }
}
?>

與以下html表單鏈接

  <?php if (isset($error)) { ?>
    <small style="color:#aa0000;"><?php echo $error;  ?> </small>
  <?php } ?>


  <form action="blog.php" method="post">
    <input type="text" name="username" placeholder="username" />
    <input type="password" name="password" placeholder="password" />
    <input type="submit" value="login" />
  </form>

Answer 1

如果實際的驗證是在admin.php中完成的，那么該action應該指向admin.php ？

  <?php if (isset($error)) { ?>
    <small style="color:#aa0000;"><?php echo $error;  ?> </small>
  <?php } ?>


  <form action="admin.php" method="post">
    <input type="text" name="username" placeholder="username" />
    <input type="password" name="password" placeholder="password" />
    <input type="submit" value="login" />
  </form>