Login

<?php

if( !empty($_POST['username']) && !empty($_POST['password'])) {
    $username=$_POST['username'];
    $password=$_POST['password'];

    $con=mysqli_connect('localhost','root','') or die(mysqli_error());
    mysqli_select_db($con, 'mydb') or die("cannot select DB");

    $sql =mysqli_query($con ,"SELECT * FROM users WHERE username='$username' AND password='$password'");
    $result=mysqli_num_rows($sql);
    if($result!=0)
    {
    while($row=mysqli_fetch_assoc($sql))
    {
    $dbusername=$row['username'];
    $dbpassword=$row['password'];
    }

    if ($username == $dbusername && $password == $dbpassword)
    {
    session_start();
    $_SESSION['sess_user']=$username;

    header("Location: upload.php");
    }
    } else {
    echo "Sorry, invalid username or password!";
    }

}
?>