<?php
if(isset($_POST['submit'])) {
  mysql_connect("localhost", "root", "pass");
  mysql_select_db("database");

  $username = $_POST['username'];
  $password = $_POST['password'];

  $username = mysql_real_escape_string($username);
  $password = mysql_real_escape_string($password);

  $password = md5($password);

  $sql = mysql_query("SELECT * FROM users WHERE username = '$username' AND password = '$password'");
  $nr = mysql_num_rows($sql);

  if($nr == 0) {
    echo "Bad login, try again";
      }else{
    while($row = mysql_fetch_array($sql)) {
      $username = $row['username'];
    }
    session_start();
    $_SESSION['lia'] = $username;
    echo "Welcome, ".$_SESSION['lia']."";
    echo "<a href='home.php'>Home page</a>";
    header('Location: home.php');
  }
}
?>