$db = mysql_connect("localhost", "root", "", "login");
 if(isset($_POST['register_btn'])) {
    $username = mysql_real_escape_string($_POST['username']);
    $email = mysql_real_escape_string($_POST['email']);
    $password = mysql_real_escape_string($_POST['password']);
    $password2 = mysql_real_escape_string($_POST['password2']);

if($password == $password2) {
      $password = md5($password);
      $sql = "INSERT INTO user(username, email, password) VALUES('$username', '$email', '$password')";
      mysqli_query($db, $sql);
      $_SESSION['message'] = "You are now logged in";
      $_SESSION['username'] = $username;
      header("location: process.php");
    }else{
      $_SESSION['message'] = "The two passwords do not match"

      ?>

<form method="post" action="register.php">
       <table>
         <tr>
            <td>Username:</td>
            <td><input type="text" name="username" class="textInput"></td>
          </tr>
          <tr>
            <td>Email:</td>
            <td><input type="email" name="email" class="textInput"></td>
          </tr>
          <tr>
            <td>Password:</td>
            <td><input type="password" name="password" class="textinput"></td>
          </tr>
          <tr>
            <td>Password again:</td>
            <td><input type="password" name="password2" class="textInput"></td>
          </tr>
          <tr>
          <td></td>
            <td><input type="submit" name="register_btn" value="Register"></td>
          </tr>
      </table>
     </form>