login.php

        <?php

            require_once('dbConfig.php');
            require_once('functions.php');

            session_start();

            if ($_SESSION['logged_in'] == true) {


                redirect('../TASK2PHP/upload.php');

            } else {

            if ((!isset($_POST['username'])) || (!isset($_POST['password'])) OR (!ctype_alnum($_POST['username'])) ) {


                    redirect('../TASK2PHP/index.php');
                    echo 'You are not logged in.';

            }

            $mysqli = @new mysqli(DB_HOSTNAME, DB_USERNAME, DB_PASSWORD, DB_DATABASE);

            if (mysqli_connect_errno()) {

            printf("Unable to login. Connection to database failed. %s", mysqli_connect_error());

            exit();

            }

            $username = $mysqli-> real_escape_string($_POST['username']);
            $password = $mysqli-> real_escape_string($_POST['password']);

            $sql = "SELECT * FROM users WHERE username = '" . $username . "' AND password = '" . $password . "'";

            $result = $mysqli-> query($sql);

            if (is_object($result) && $result->num_rows == 1) {


            $_SESSION['logged_in'] = true;

            redirect('../TASK2PHP/upload.php');
            echo 'You are now logged in ' , $username;



            } else {


            redirect('../TASK2PHP/index.php');


            }


        }


        ?>