会话id没有显示错误消息注意:未定义的索引:UserID也如果我重定向非登录用户，我将不会登录到主页。这是我的文件，谁能告诉我哪里出错了?
这里是主页:
<?php
require ("insert.php");
session_start();
if (isset($_SESSION["UserID"])){
}
else {
echo "session not transferring";
}
?>
<!DOCTYPE html>
<html lang="en-US">
<head>
<title>AMSadler</title>
<meta charset="utf-8">
<meta name="description" content="description of webpage">
<meta name="keywords" content="keywords go here">
<meta name="author" content="Anthony">
<link rel="stylesheet" href="css/style.css">
<link rel="stylesheet" href="css/home.css">
<link rel="icon" href="img/favicon.png" sizes="16x16" type="image/png">
</head>
<body>
<div class="header">
<div id="logo">
<a href="index.html"><img src="img/logo.png" alt="logo" title="AMSadler.com"/></a>
</div>
<div id="headertop">
<div id="pagetitle">
<a href="home.php">HOME</a>
</div>
<div id="pagetitle2">
<a href="profile.php">PROFILE</a>
</div>
<div id="pagetitle3">
<h4>Welcome:<?php echo $_SESSION{"UserID"};?>to your page</h4>
</div>
</div>
</div>
<div class="wrapper">
<div class="leftsidebar">
<ul>
<li><a href="home.php">blah</a></li>
<li><a href="#">blah</a></li>
<li><a href="#">blah</a></li>
<li><a href="#">blah</a></li>
<li><a href="#">blah</a></li>
<li><a href="#">blah</a></li>
<li><a href="#">blah</a></li>
<li><a href="#">blah</a></li>
<li><a href="#">blah</a></li>
<li><a href="#">blah</a></li>
</ul>
</div>
<div class="main">
<div id="maintop">
<div id="textboxwrap">
<textarea name="text" id="styled"rows="5" cols="80" placeholder="Write something here.">
</textarea>
</div>
<div id="postbutton">
<input type="submit" name="post" value="Post" />
</div>
</div>
<div id="mainbottom1">
<div ="mainbottomwrap">
Your posts will go here.<br>Your posts will go here.<br>Your posts will go here.<br>Your posts will go here.<br>
Your posts will go here.<br>Your posts will go here.<br>Your posts will go here.<br>Your posts will go here.<br>
Your posts will go here.<br>Your posts will go here.<br>Your posts will go here.<br>Your posts will go here.<br>
Your posts will go here.<br>Your posts will go here.<br>
</div>
</div>
</div>
<div class="rightsidebar">
<div id="profilecontainer">
<img src="img/profile.png" alt="Upload a profile pic" title="profile pic" />
</div>
<div id="box">
<a href="#">blah</a><br>
<a href="#">blah</a><br>
<a href="#">blah</a><br>
<a href="#">blah</a><br>
<a href="#">blah</a><br>
<a href="#">blah</a><br>
<a href="#">blah</a><br>
<a href="#">blah</a>
</div>
</div>
</div>
</body>
</html>
==================================================================这是登录页面。+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
<?php require ("insert.php"); ?>
<?php
if(isset($_POST[ 'Login' ]))
{
$email= mysqli_real_escape_string($con, $_POST ['email']);
$pswrd= mysqli_real_escape_string($con, $_POST ['pswrd']);
$result = $con->query (" select * from users where email='$email' AND pswrd='$pswrd' ");
$row = $result->fetch_array(MYSQLI_BOTH);
session_start();
$_SESSION["User ID"] = $row['UserID'];
header ('Location: home.php');
}
?>
<!DOCTYPE html>
<html lang="en-US">
<head>
<title>AMSadler login</title>
<meta charset="utf-8">
<meta name="description" content="description of webpage">
<meta name="keywords" content="keywords go here">
<meta name="author" content="Anthony">
<link rel="stylesheet" href="css/style.css">
<link rel="stylesheet" href="css/login.css">
<link rel="index" href="index.php">
<link rel="icon" href="img/favicon.png" sizes="16x16" type="image/png">
</head>
<body>
<div class="header">
<div id="logo">
<a href="index.html"><img src="img/logo.png" alt="logo" title="AMSadler.com"/></a>
</div>
<div id="signup">
<button type="button"><a href="signup.php">Sign up</a></button>
</div>
</div>
<div id="login">
<form action="home.php" method="post">
<input type="text" name="email" placeholder="Email address">
<br>
<input type="password" name="password" placeholder="Password">
<br>
<input id="Login" type="submit" name="Login" value="Login">
</form>
</div>
<footer>
<div id="copyright">
<p>© Copyright 2015</p>
</div>
</footer>
</body>
</html>
我当然希望你只是张贴一个例子，你不存储明文密码值…无论如何…
我没有足够的代表给@Bono添加评论，但是除了他的发现之外，您还使用了以下POST:
$_POST ['pswrd']
但是在你的表单上，你有:
<input type="password" name="password" placeholder="Password">
需要更改密码的表单名或您正在查找的POST。
在你的登录页面中，你是这样分配变量的:
$_SESSION["User ID"] = $row['UserID'];
但是在首页你要找的是UserID。
改变:
$_SESSION["User ID"] = $row['UserID'];
$_SESSION["UserID"] = $row['UserID'];
你得到错误的点是你在HTML中的使用，你说:
<h4>Welcome:<?php echo $_SESSION{"UserID"};?>to your page</h4>
在第一个实例中，您正在使用isset()，但在这里，您突然假设它在那里并准备使用。无论哪种方式，您都应该编辑User ID变量，这样就可以停止抛出错误。您可能还想在这里添加一个isset()语句。
注:还要注意维克多·佩雷斯关于你的密码的回答。并且不要将它们存储为纯文本。你实际上只是在检查数据库中的POST密码，这是不好的。此外，我可能会建议您远离使用这样的查询，并开始使用准备好的语句。