我很新于PHP，尝试在互联网上找到了答案，但最终失败。我已经查看了无数的示例，但人们似乎都有不同于我系统的登录方式，这让我很难理解。
以下是我目前的代码：
index.html
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Video for Education Log In</title>
<link rel="stylesheet" type="text/css" href="style.css" />
</head>
<body>
<div id="wrapper">
<div id="header">
<div id="logo">
videoedu.edu </div>
<div id="menu">
<ul>
<li><a href="account.html" class="menua">Create Account</a></li>
<li><a href="about.html" class="menua">About Us</a></li>
</ul>
</div>
</div>
<br><br><br><br>
<div id="page">
<div id="content">
<h2>Video for Education helps you connect and share with the videos in your life.</h2>
<h3>Upload Share Create Using video for your education purposes. Lecturers Welcome
Upload Share Create Using video for your education purposes. Lecturers Welcome
Upload Share Create Using video for your education purposes. Lecturers Welcome</h3>
<div class= "form">
<form name="login" method="post" action="checklogin.php">
Username: <input type="text" name="myusername" id="myusername" class="textb"/><br />
Password : <input type="password" name="mypassword" id="mypassword" class="textb"/><br />
<br>
<input type="submit" name="login" value="Login" id="login" class="texta" />
</form>
</div>
</div>
</div>
</div>
</body>
</html>
checklogin.php
<?php
$host = "localhost";
$username = "root";
$password = "";
$db_name = "test";
$tbl_name = "members";
mysql_connect("$host", "$username", "$password")or die("Cannot connect.");
mysql_select_db("$db_name")or die("Cannot select DB.");
$myusername=$_POST["myusername"];
$mypassword=$_POST["mypassword"];
if ($myusername&&$mypassword)
{
$myusername = stripslashes($myusername);
$mypassword = stripslashes($mypassword);
$myusername = mysql_real_escape_string($myusername);
$mypassword = mysql_real_escape_string($mypassword);
$sql = "SELECT * FROM $tbl_name WHERE username='$myusername' and password='$mypassword'";
$result = mysql_query($sql);
$count = mysql_num_rows($result);
if($count == 1){
session_register("myusername");
session_register("mypassword");
header("location:login_success.php");
}
else
{
echo "Wrong Username or Password";
}
}
else
echo "You have left one or more fields blank.";
?>
login_success.php
<?
session_start();
if( !isset( $_SESSION['myusername'] ) ){
header("location:account.html");
}
echo "Welcome, ".$_SESSION['myusername']." - You are now logged in.<br>";
echo "<a href=logout.php>Logout</a>"
?>
<html>
<body>
</body>
</html>
logout.php
<?php
session_start();
session_destroy();
echo "You have been logged out, <a href='index.php'>click here</a> to return."
?>
我已经尝试将此内容插入到index.html中，并将文件名更改为index.php。
$submit = $_POST["login"];
if($submit)
{
}
...但它始终在页面底部显示一个错误信息（“用户名或密码错误”）。
我希望当用户输入错误的用户名或密码，或者留空必填字段时，错误信息将弹出在同一页上，而不是跳转到一个新的丑陋的PHP页面，并在左上角显示错误信息。