<?php

SESSION_START();

$servername = "localhost";
$username = "MY USERNAME";
$password = "MY PASSWORD";
$dbname = "MY USERNAME";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

$username = $_POST['usernameinput'];
$password= $_POST['passwordinput'];
$_SESSION["loggedin"] = false   ;

echo ($username);
echo ($password);

$result = mysqli_query($conn,"SELECT `user-id` FROM `users` WHERE `username`     = '" . $username. "' AND `password` = '" . $password. "' ");

if (!$result) {
    die(mysqli_error($conn));
    }

if(mysqli_num_rows($result) > 0) {
    $row = mysqli_fetch_array($result);
    return $row['ID'];
    $_SESSION["loggedin"] = true;
 }

print_r($_SESSION);

$conn->close();
?>