$query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
$results = mysqli_query($db, $query);
if (mysqli_num_rows($results) == 1) {


  $_SESSION['email'] = $email;
  $_SESSION['username'] = $username;
  $_SESSION['success'] = "You are now logged in";
  header('location: index.php');

<?php
// Echo session variables that were set on previous page
echo "Your email is: " . $_SESSION['email'] . "<br>";
echo "Your username is: " . $_SESSION['username'] . "";
?>