Question

当我在网站上传网站后重新加载网站时，我的网站上出现以下错误：

警告：session_start（）：无法发送会话缓存限制器 - 标头已发送（输出开始于 /data/userfiles/websites/lagersystem/login.php:1)in 第36行/data/userfiles/websites/lagersystem/login.php

我不知道如何解决这个问题。

这是我的源代码：

<html>
    <head>
        <title>Login</title>
            <meta name="viewport" content="width=device-width, initial-scale=1">
            <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
        <link rel="icon" type="favicon.gif" href="favicon.gif" sizes="256x256">
    </head>

<body>


<div class="p-3 mb-2 bg-secondary text-white">
<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <a class="navbar-brand" href="index.php"><img src='favicon-64.gif'/></a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>

  <div class="collapse navbar-collapse" id="navbarSupportedContent">
    <ul class="navbar-nav mr-auto">
      <li class="nav-item active">
        <a class="nav-link" href="index.php">Home<span class="sr-only">(current)</span></a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="add.php">Hinzufügen</a>
      </li>
       <li class="nav-item">
        <a class="nav-link" href="login.php">Admin</a>
      </li>
    </ul>
     </div>
</nav>
</div>

<?php 
session_start();
$pdo = new PDO('mysql:host=localhost;dbname=', '', '');

if(isset($_GET['login'])) {
    $email = $_POST['email'];
    $passwort = $_POST['passwort'];

    $statement = $pdo->prepare("SELECT * FROM ls_users WHERE email = :email");
    $result = $statement->execute(array('email' => $email));
    $user = $statement->fetch();

    //Überprüfung des Passworts
    if ($user !== false && password_verify($passwort, $user['passwort'])) {
        $_SESSION['userid'] = $user['id'];
        die('<div class="text-center">Login erfolgreich. Weiter zu <a href="sicherheit.php">internen Bereich</a></div>');
    } else {
        $errorMessage = "E-Mail oder Passwort falsch!<br>";
    }

}
?>

<?php 
if(isset($errorMessage)) {
    echo $errorMessage;
}
?>

 <div class="row align-items-center justify-content-center">
    <div class="text-center">

<form action="?login=1" method="post">
E-Mail:<br>
<input class="form-control" type="email" size="40" maxlength="250" name="email"><br><br>

Dein Passwort:<br>
<input class="form-control" type="password" size="40"  maxlength="250" name="passwort"><br>

<input class="form-control" type="submit" value="Anmelden">

</form> 

<br />
<br />
</div>
</div>




<div class="p-3 mb-2 bg-secondary text-white">

<div class="row">
    <div class="col">

        <div class="text-center">

            <a href="index.php" class="btn btn-dark">Aktualisieren</a>

        </div>
    </div>
    <div class="col">

        <div class="text-center">

            <a href="fehler.php" class="btn btn-danger">Fehlermeldung</a>

        </div>
    </div>
</div>

</div>

<div class="p-3 mb-2 bg-secondary text-white">

<footer class="mainfooter" role="contentinfo">
 <div class="footer-top p-y-2">
    <div class="container-fluid">

    </div>
  </div>
  <div class="footer-middle">
  <div class="container">
 <div class="footer-bottom">
    <div class="container">
      <div class="row">
        <div class="col">
          <!--Footer Bottom-->
           <p class="text-center">&copy; 2018 - All rights reserved.</p>
        </div>
      </div>
    </div>
  </div>
</footer>
</div>

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>

</body>

</html>

谢谢。

Answer 1

您必须使用

启动该文件

<?php 
session_start();

原因是会话通过cookie工作（如果客户端从不在那里，PHP会将随机数作为cookie发送。然后，每当客户端回来时，他发送该cookie并且PHP可以查找$_SESSION对于那个用户）。

问题是在任何HTML经过之前必须在标题中发送cookie，所以如果你做了类似的事情：

<html> <?php session_start();?>

PHP会读取你的文件，看到你写了“”，认为没有更多的标题需要写，并从其余部分开始。然后当它点击session_start时，它就不能再返回并给你错误。

像这样：

<?php session_start();?>
<html>
    <head>
        <title>Login</title>
            <meta name="viewport" content="width=device-width, initial-scale=1">
            <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
        <link rel="icon" type="favicon.gif" href="favicon.gif" sizes="256x256">
    </head>

<body>


<div class="p-3 mb-2 bg-secondary text-white">
<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <a class="navbar-brand" href="index.php"><img src='favicon-64.gif'/></a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>

  <div class="collapse navbar-collapse" id="navbarSupportedContent">
    <ul class="navbar-nav mr-auto">
      <li class="nav-item active">
        <a class="nav-link" href="index.php">Home<span class="sr-only">(current)</span></a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="add.php">Hinzufügen</a>
      </li>
       <li class="nav-item">
        <a class="nav-link" href="login.php">Admin</a>
      </li>
    </ul>
     </div>
</nav>
</div>

<?php 

$pdo = new PDO('mysql:host=localhost;dbname=', '', '');

if(isset($_GET['login'])) {
    $email = $_POST['email'];
    $passwort = $_POST['passwort'];

    $statement = $pdo->prepare("SELECT * FROM ls_users WHERE email = :email");
    $result = $statement->execute(array('email' => $email));
    $user = $statement->fetch();

    //Überprüfung des Passworts
    if ($user !== false && password_verify($passwort, $user['passwort'])) {
        $_SESSION['userid'] = $user['id'];
        die('<div class="text-center">Login erfolgreich. Weiter zu <a href="sicherheit.php">internen Bereich</a></div>');
    } else {
        $errorMessage = "E-Mail oder Passwort falsch!<br>";
    }

}
?>

<?php 
if(isset($errorMessage)) {
    echo $errorMessage;
}
?>

 <div class="row align-items-center justify-content-center">
    <div class="text-center">

<form action="?login=1" method="post">
E-Mail:<br>
<input class="form-control" type="email" size="40" maxlength="250" name="email"><br><br>

Dein Passwort:<br>
<input class="form-control" type="password" size="40"  maxlength="250" name="passwort"><br>

<input class="form-control" type="submit" value="Anmelden">

</form> 

<br />
<br />
</div>
</div>




<div class="p-3 mb-2 bg-secondary text-white">

<div class="row">
    <div class="col">

        <div class="text-center">

            <a href="index.php" class="btn btn-dark">Aktualisieren</a>

        </div>
    </div>
    <div class="col">

        <div class="text-center">

            <a href="fehler.php" class="btn btn-danger">Fehlermeldung</a>

        </div>
    </div>
</div>

</div>

<div class="p-3 mb-2 bg-secondary text-white">

<footer class="mainfooter" role="contentinfo">
 <div class="footer-top p-y-2">
    <div class="container-fluid">

    </div>
  </div>
  <div class="footer-middle">
  <div class="container">
 <div class="footer-bottom">
    <div class="container">
      <div class="row">
        <div class="col">
          <!--Footer Bottom-->
           <p class="text-center">&copy; 2018 - All rights reserved.</p>
        </div>
      </div>
    </div>
  </div>
</footer>
</div>

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>

</body>

</html>

会话启动错误但不知道如何解决

1 个答案: