Question

我已经看过很多次这个问题，但是有了所有这些答案，我仍然无法解决问题。

我有这个html登录表单页面。使用正确的用户名和密码单击“登录”后，我想重定向到登录墙后面的下一页。错误消息有效，但重定向导致重新加载当前页面。重新加载后，用于显示错误消息的脚本也将损坏。

<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, shrink-to-fit=no">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.3/css/bootstrap.min.css">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
    <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Source+Sans+Pro">
    <link rel="stylesheet" href="assets/css/styles.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>    
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.3/js/bootstrap.bundle.min.js"></script>
</head>

<body>
  <form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" method="post">
    <button class="btn btn-primary button_login" type="submit">Log in</button>
  </form>
</body>
<?php
// Initialize the session
session_start();
 
// Check if the user is already logged in, if yes then redirect him to welcome page
if(isset($_SESSION["loggedin"]) && $_SESSION["loggedin"] === true){
    header("location: welcome.php");
    exit;
}
 
// Include config file
require_once "config.php";
 
// Define variables and initialize with empty values
$username = $password = "";
$username_err = $password_err = "";
 
// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){
 
    // Check if username is empty
    if(empty(trim($_POST["username"]))){
        $username_err = "Please enter username.";
    } else{
        $username = trim($_POST["username"]);
    }
    
    // Check if password is empty
    if(empty(trim($_POST["password"]))){
        $password_err = "Please enter your password.";
    } else{
        $password = trim($_POST["password"]);
    }
    
    // Validate credentials
    if(empty($username_err) && empty($password_err)){
        // Prepare a select statement
        $sql = "SELECT id, username, password FROM users WHERE username = ?";
        
        if($stmt = mysqli_prepare($link, $sql)){
            // Bind variables to the prepared statement as parameters
            mysqli_stmt_bind_param($stmt, "s", $param_username);
            
            // Set parameters
            $param_username = $username;
            
            // Attempt to execute the prepared statement
            if(mysqli_stmt_execute($stmt)){
                // Store result
                mysqli_stmt_store_result($stmt);
                
                // Check if username exists, if yes then verify password
                if(mysqli_stmt_num_rows($stmt) == 1){                    
                    // Bind result variables
                    mysqli_stmt_bind_result($stmt, $id, $username, $hashed_password);
                    if(mysqli_stmt_fetch($stmt)){
                        if(password_verify($password, $hashed_password)){
                            // Password is correct, so start a new session
                            session_start();
                            
                            // Store data in session variables
                            $_SESSION["loggedin"] = true;
                            $_SESSION["id"] = $id;
                            $_SESSION["username"] = $username;                            
                            
                            // Redirect user to welcome page
                            header("Location: http://www.google.com/");
                            exit;
                        } else {
                            echo '<script>console.log("Error: Password incorrect"); document.getElementById("password_alert").style.display = "block";</script>';
                        }
                    }
                } else{
                    echo '<script>console.log("Error: Username incorrect"); document.getElementById("username_alert").style.display = "block";</script>';
                }
            } else{
                echo "Oops! Something went wrong. Please try again later.";
            }
        }
        
        // Close statement
        mysqli_stmt_close($stmt);
    }
    
    // Close connection
    mysqli_close($link);
}
?>
</html>

Answer 1

您需要移动重定向代码，以便在页面上生成任何输出之前触发它。像这样：

<?php
// Initialize the session
session_start();

// Check if the user is already logged in, if yes then redirect him to welcome page
if(isset($_SESSION["loggedin"]) && $_SESSION["loggedin"] === true){
    header("location: welcome.php");
    exit;
}
?>

<!DOCTYPE html>
<html>
...

其原因是重定向方法依赖于将标头发送到客户端。简而言之，输出开始后就无法发送标头。因此，必须在发送任何输出之前进行所有重定向。这也可以通过使用输出缓冲区来实现。 What is output buffering?

PHP标头重定向重新加载页面，而不是重定向

1 个答案: