PHP MySQL Login Processor

<?php
if (isset($_POST['submit'])) {
    $username = $_POST['username'];
    $password = $_POST['password'];

    // processing remember me option and setting cookie with long expiry date
    if (isset($_POST['remember'])) {
        session_set_cookie_params('604800'); //one week (value in seconds)
        session_regenerate_id(true);
    }

    $mysqli = new mysqli(DB_HOST, DB_USER, DB_PASS, DB_NAME);
    # check connection
    if ($mysqli->connect_errno) {
        echo "MySQL error no {$mysqli->connect_errno} : {$mysqli->connect_error}";
        exit();
    }

    $sql = "SELECT * from users WHERE username LIKE '{$username}' AND password LIKE '{$password}' LIMIT 1";
    $result = $mysqli->query($sql);

    if ($result->num_rows != 1) {
        echo "Error: Invalid username/password combination";
    }
    else {
        $user = $result->fetch_array();
        $_SESSION['user_id'] = $user['id'];
        $_SESSION['username'] = $user['username'];

        $timestamp = time();
        $sql = "UPDATE users SET status={$timestamp} WHERE id={$_SESSION['user_id']}";
        $result = $mysqli->query($sql);

        redirect_to("index.php?id={$_SESSION['user_id']}");
    }
}
if (isset($_GET['msg'])) {
    echo "" . $_GET['msg'] . "";
}
if (logged_in() == true) {
    echo "You have Logged in successfully. Click here to go to the main page";
}
else {
    echo "Oh! No account? Register here!";
}
?>