登录索引表单不适用于登录.php如果我使用 header(）函数

我是php的初学者。我正在尝试制作登录表单(索引1.php(。如果我将其重定向到登录.php在表单标签中使用"操作"属性，它可以正常工作。但我也想对相同的索引形式进行一些验证。因此，我使用标头函数而不是"操作"属性将其重定向到"登录.php"。

无论我是否输入正确的用户名和密码，在执行最后一个登录.php(//该用户不存在(时，它都会给我无效变量"$username"和"$password"的错误。请帮助我知道我的代码出了什么问题，我应该怎么做才能让它在登录.php上运行？

这是索引 1 的代码.php

  <!DOCTYPE HTML>
<html>
<head><br>
<style>
.error {color: #FF0000;}
</style>
</head>
<body style="font-family: verdana, sans-serif;";>   
<hr />
<div style="width: 77%; height: 300px; padding: 30px; border: 5px solid #e3e3e3; background-color: #F8F8F8 ; color: #000; margin: 100px;" align="center">
 <br>
<?php
 $username=$password="";
 $Err="";
 if($_SERVER['REQUEST_METHOD']== "POST")
 {  
     $valid = true;
     if ((empty($_POST["username"])) || (empty($_POST["password"])))
    {
      $Err = "Please Enter your username and password";
      $valid = false; 
    }
   else 
    {
      $username = test_input($_POST["username"]);
      $password = test_input($_POST["password"]);
    }

   if($valid)
   { 
     header("location:login.php");
   }

 } 
 function test_input($data) 
{
   $data = trim($data);
   $data = stripslashes($data);
   $data = htmlspecialchars($data);
   return $data;
}
?>
 <span class="error"><?php echo $Err; ?></span>
 <h2>Login</h2>
 <form action="menubar.php?page=index1" method="post">
      <font size="3">Username:<input type="text" name="username" style="padding: 4px;"/><p>
      Password: <input type="password" name="password" style="padding: 4px;"/><p>
                 <input type="submit" value="Login" style="padding: 4px; width: 5em; height: 1.9em;"/></font>
    </form>
     <h5> No Account?<a href="menubar.php?page=register">Register!</a></h5>
    </div>
</body>
</html>

这是登录代码.php。

<?php
session_start();
$username=$_POST["username"];
$password=$_POST["password"];
$message[]="Fill up both username and password";
    $connect=mysql_connect("localhost","root","") or die("Couldnt connect to Database");
    mysql_select_db("login") or die("Couldnt find Database");
    $query = mysql_query("SELECT * FROM users WHERE username='$username'");
    $numrows = mysql_num_rows($query);
    if($numrows!==0)//username exists in database
    {
        while($row = mysql_fetch_assoc($query))
        {
            $dbusername = $row['username'];
            $dbpassword = $row['password'];
        }
        if($username==$dbusername&&$password==$dbpassword)//valid username and password
        {
            $_SESSION['username'] = $username;
           header("Location: menubar.php?page=home");
        }
        else//incorrect password or username
        die("incorrect password or username");
    }
    else//that user doesnt exit
    die("that user doesnt exit");//

?>

好的，现在我用了"sqli"代替

这是更新的登录.php代码

<?php
session_start();
$username=$_POST["username"];
$password=$_POST["password"];
$message[]="Fill up both username and password";
    $connect=mysqli_connect("localhost","root","") or die("Couldnt connect to Database");
    mysqli_select_db($connect,'login') or die("Couldnt find Database");
    $query = mysqli_query("SELECT * FROM users WHERE username='$username'");
    $numrows = mysqli_num_rows($query);
    if($numrows!==0)//username exists in database
    {
        while($row = mysqli_fetch_assoc($query))
        {
            $dbusername = $row['username'];
            $dbpassword = $row['password'];
        }
        if($username==$dbusername&&$password==$dbpassword)//valid username and password
        {
            $_SESSION['username'] = $username;
           header("Location: menubar.php?page=home");
        }
        else//incorrect password or username
        die("incorrect password or username");
    }
    else//that user doesnt exit
    die("that user doesnt exit");//

?>

现在更新后我没有收到无效变量的错误.但它仍然无法正常进行。无论我是否输入正确的用户名和密码，它都在执行最里面的，即(//有效的用户名和密码(

谢谢。。。。

正如已经建议的那样，将所有PHP代码放在任何HTML输出之前
您没有使用 header(( 函数传递 POST 变量，您可以使用会话或 POST 到同一页面

所以你的代码将是这样的

<?php
 $username=$password="";
 $Err="";
 if($_SERVER['REQUEST_METHOD']== "POST")
 {  
     $valid = true;
     if ((empty($_POST["username"])) || (empty($_POST["password"])))
    {
      $Err = "Please Enter your username and password";
      $valid = false; 
    }
   else 
    {
      $username = test_input($_POST["username"]);
      $password = test_input($_POST["password"]);
    }

   if($valid)
   { 
     include("login.php");
   }

 } 
 function test_input($data) 
{
   $data = trim($data);
   $data = stripslashes($data);
   $data = htmlspecialchars($data);
   return $data;
}
?>
  <!DOCTYPE HTML>
<html>
<head><br>
<style>
.error {color: #FF0000;}
</style>
</head>
<body style="font-family: verdana, sans-serif;";>   
<hr />
<div style="width: 77%; height: 300px; padding: 30px; border: 5px solid #e3e3e3; background-color: #F8F8F8 ; color: #000; margin: 100px;" align="center">
 <br>
 <span class="error"><?php echo $Err; ?></span>
 <h2>Login</h2>
 <form action="menubar.php?page=index1" method="post">
      <font size="3">Username:<input type="text" name="username" style="padding: 4px;"/><p>
      Password: <input type="password" name="password" style="padding: 4px;"/><p>
                 <input type="submit" value="Login" style="padding: 4px; width: 5em; height: 1.9em;"/></font>
    </form>
     <h5> No Account?<a href="menubar.php?page=register">Register!</a></h5>
    </div>
</body>
</html>

代码中的问题在于 login.php ，$_POST["username"] 并且从未设置过$_POST["password"]，所以你能做的最好的事情就是不使用header，只使用require_once

<!DOCTYPE HTML>
<html>
<head><br>
<style>
.error {color: #FF0000;}
</style>
</head>
<body style="font-family: verdana, sans-serif;";>   
<hr />
<div style="width: 77%; height: 300px; padding: 30px; border: 5px solid #e3e3e3; background-color: #F8F8F8 ; color: #000; margin: 100px;" align="center">
 <br>
<?php
 $username=$password="";
 $Err="";
 if($_SERVER['REQUEST_METHOD']== "POST"){  
     $valid = true;
     if ((empty($_POST["username"])) || (empty($_POST["password"]))){
      $Err = "Please Enter your username and password";
      $valid = false; 
    }else{
      $username = test_input($_POST["username"]);
      $password = test_input($_POST["password"]);
    }

   if($valid)
   { 
     require_once('login.php');
   }

} 
 function test_input($data) {
   $data = trim($data);
   $data = stripslashes($data);
   $data = htmlspecialchars($data);
   return $data;
}
?>
 <span class="error"><?php echo $Err; ?></span>
 <h2>Login</h2>
 <form action="menubar.php?page=index1" method="post">
      <font size="3">Username:<input type="text" name="username" style="padding: 4px;"/><p>
      Password: <input type="password" name="password" style="padding: 4px;"/><p>
                 <input type="submit" value="Login" style="padding: 4px; width: 5em; height: 1.9em;"/></font>
    </form>
     <h5> No Account?<a href="menubar.php?page=register">Register!</a></h5>
    </div>
</body>
</html>

非常重要的是要注意，在设置标头之前，您应该没有向客户端发送任何输出-

header("Location: menubar.php?page=home");//or login.php

因此，在发送任何数据之前，请验证您的数据并设置标头，如果数据无效，则发送正常数据。

更新：以下是完整的测试代码

索引1.php

<?php session_start();?>
<!DOCTYPE HTML>
<html>
<head><br>
<style>
    .error {color: #FF0000;}
</style>
</head>
<body style="font-family: verdana, sans-serif;";>   
<hr />
<div style="width: 77%; height: 300px; padding: 30px; border: 5px solid #e3e3e3; background-color: #F8F8F8 ; color: #000; margin: 100px;" align="center">
 <br>
 <?php if(isset($_SESSION['message'])){ echo  "<span class='error'>".$_SESSION['message']."</span>"; $_SESSION['message']=null;}?>
 <h2>Login</h2>
 <form action="login.php" method="post">
         <font size="3">Username:<input type="text" name="username" style="padding: 4px;"/><p>
  Password: <input type="password" name="password" style="padding: 4px;"/><p>
             <input type="submit" value="Login" style="padding: 4px; width: 5em; height: 1.9em;"/></font>
</form>
 <h5> No Account?<a href="menubar.php?page=register">Register!</a></h5>
</div>
</body>
</html>

<?php
session_start();
$username=$password="";
$Err="";
if($_SERVER['REQUEST_METHOD']== "POST")
 {
    $valid = true;
 if ((empty($_POST["username"])) || (empty($_POST["password"])))
{
  $Err = "Please Enter your username and password";
  $valid = false; 
}
else 
{
  $username = test_input($_POST["username"]);
  $password = test_input($_POST["password"]);
}
   if($valid) {
    $valid = false;//reset $valid value to validate for Database test
    //$username=$_POST["username"];
    //$password=$_POST["password"];
    //$message[]="Fill up both username and password";
    $connect=mysqli_connect("localhost","root","") or die("Couldnt connect to Database");
    mysqli_select_db($connect,'login') or die("Couldnt find Database");
//Note: mysqi_query() returns results of query
    $result = mysqli_query($connect, "SELECT * FROM users WHERE username='$username'");//update here pass the $connect parameter
    $numrows = mysqli_num_rows($result);//change here
if($numrows!==0)//username exists in database
{
    $dbusername = null;//move it up for visibility after while block
    $dbpassword = null;
    while($row = mysqli_fetch_assoc($result))//Note here pass the result
    {
        $dbusername = $row['username'];
        $dbpassword = $row['password'];
    }
    if($username == $dbusername&&$password==$dbpassword)//valid username and password
    {
        $_SESSION['username'] = $username;
       header("Location: menubar.php?page=home");//the landing page
       die();
    }
    else{
        //incorrect password or username
        $Err = "incorrect password or username";
        $valid = false;
    }
}
else {
    //that user doesnt exit
    $Err = "that user doesnt exit";
    $valid = false;
}   
 //header("location:index.php");
}   
if(!$valid) {
    $_SESSION['message'] = $Err;//Put the message in $_SESSION variable
    header("location:index1.php");
}
 }
function test_input($data) 
{
   $data = trim($data);
   $data = stripslashes($data);
   $data = htmlspecialchars($data);
   return $data;
}
?>

菜单栏.php

<?php
session_start();
$page=isset($_GET["page"])?$_GET["page"]:"";
if(isset($page)) {
    header("location: ".$page.".php");
} else {
    header("location: 404.php");
}
?>

这是因为您有一个输出：

?>
<?php

导致空行输出。

在发送任何实际输出之前，必须通过普通 HTML 标记、文件中的空行或从 PHP 调用 header((

合并所有PHP代码，并确保文件开头没有任何空格。

同样在header('location: index.php');之后添加exit();如果您有任何其他脚本在下面。

还要将您的重定向标头移到最后一个 if 之后。

登录索引表单不适用于登录.php如果我使用 header(） 函数

Login index form is not working with login.php if i use header() function