PHP登录工作脱机，但在线不工作

Question

大家好，我是新来的PHP。我检查了W3C，并获得了一些很好的提示。但是，我的登录代码面临着一个小的挑战。它显示PHP警告：无法修改标头信息 - 已发送的标头(输出启用in/home/perspect/public_html/jst/dbcon.php:2(以下是我的索引页;

<?php
session_start();
include_once 'includes/dbcon.php';
if(isset($_SESSION['user'])!="")
{
    header("Location: candidate_list.php");
}
if(isset($_POST['btn-login']))
{
    $username = mysqli_real_escape_string($con, $_POST['username']);
    $password = mysqli_real_escape_string($con, $_POST['password']);
    $stat = 'notvoted';
    $res=mysqli_query($con,"SELECT * FROM students WHERE username='$username' AND status='$stat'");
    $row=mysqli_fetch_array($res);
    if($row['password']==md5($password))
    {
        $_SESSION['user'] = $row['user_id'];
        header("Location: candidate_list.php");
    } 
    else
    {
        ?>
        <script>alert('wrong details');</script>
        <?php
    } 
}
?>
<!-- Login Box -->
                            <div class="col-md-6 col-md-offset-3 col-sm-offset-3">
                                <form class="login-page" action="" method="post">
                                    <div class="login-header margin-bottom-30">
                                        <h2>Login</h2>
                                    </div>
                                    <div class="input-group margin-bottom-20">
                                        <span class="input-group-addon">
                                            <i class="fa fa-user"></i>
                                        </span>
                                        <input placeholder="VIN" name="username" class="form-control" type="text">
                                    </div>
                                    <div class="input-group margin-bottom-20">
                                        <span class="input-group-addon">
                                            <i class="fa fa-lock"></i>
                                        </span>
                                        <input placeholder="Password" name="password" class="form-control" type="password">
                                    </div>
                                    <div class="row">
                                        <div class="col-md-6">
                                            <button class="btn btn-primary pull-right" type="submit" name="btn-login">Login</button>
                                        </div>
                                    </div>
                                    <p> 
                                </form>
                            </div>
                            <!-- End Login Box -->

我的cantidate_list.php代码是;

<?php
session_start();
include_once 'includes/dbcon.php';
if(!isset($_SESSION['user']))
{
    header("Location: index.php");
}
$res=mysqli_query($con, "SELECT * FROM students WHERE user_id=".$_SESSION['user']);
$userRow=mysqli_fetch_array($res);
?>

我的dbcon是

  <?php
$con=mysqli_connect("xxx","xxx","xxxx","xxx");
// Check connection
if (mysqli_connect_errno()) {
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
?>

谢谢您的帮助。

Answer 1

此类型的PHP警告一旦您在标头重定向之前回声时就会出现。

如果您仍然想重定向，则可以使用ob_start或可以使用javascript

window.location.href =路径