HTML格式无法在Firefox

Question

I have just started learning PHP and I cant seem to to work like this is not going to welcome.php please help? Thankyou for your help as I have litterally put my head into this :(

$user=$_POST['user'];
$pass=$_POST['pass'];


$que ="SELECT * FROM users WHERE username='$user' and password='$pass'";
$res=mysql_query($que);

    $c=mysql_num_rows($res);

    if($c==1){
    $_SESSION['user'] = $user; 
    header("location: welcome.php");
    }
    else {
    header("location: empty.php");
    }
    ?>




        <form name="myform" method="POST" action="login.php">


         <input name="username" type="text" id="username">

         <input name="pass" input type="password" id="pass">

         <input type="submit" name="Submit" value="Login">

        </form>

Answer 1

Try this please:

      <?php
    session_start(); // You need this if you use a session    
        $user = mysql_escape_string($_POST['user']); // Defend from SQL Injection
            $pass = mysql_escape_string($_POST['pass']);

            if(isset($_POST['Submit']))
{
            $que = "SELECT * FROM users WHERE username='$user' and password='$pass';";
            $res = mysql_query($que);

                $c = mysql_num_rows($res);

                if($c==1){ // if you want use a session you need add session_start();
                $_SESSION['user'] = $user; 
                header("location: welcome.php");
                }
                else {
                header("location: empty.php");
                }
}
                ?>




                    <form name="myform" method="POST" action="login.php">


                     <input name="username" type="text" id="username">

                     <input name="pass" type="password" id="pass">

                     <input type="submit" name="Submit" value="Login">

                    </form>

Answer 2

If you have properly used session_start(); It has already been mentioned where you have messed up, I will however post it for you so you can copy/paste and see it for yourself :) Furthermore, Beware of SQL Injection/XSS Study PDO/msqli

    <?php 
        session_start();
if(isset($_POST['Submit']){
        $user=$_POST['user'];
        $pass=$_POST['pass'];


        $que ="SELECT * FROM users WHERE username='$user' and password='$pass'";
        $res=mysql_query($que);

            $c=mysql_num_rows($res);

            if($c==1){
            $_SESSION['user'] = $user; 
            header("location: welcome.php");
            }
            else {
            header("location: empty.php");
            }

    }
    ?>

            <form name="myform" method="POST" action="login.php">


             <input name="user" type="text">

             <input name="pass" input type="password">

             <input type="submit" name="Submit" value="Login">

            </form>