# MySQLi Code Review for methods and functions used

I made my first script of MySQLi. I have just learnt it from 3rd party website. So, I am not sure i am using functions which are not deprecated or outdated. I should start to practice good scripts to access databases. So, I have posted here. Any mistake you see, please point it out.

<?php

include "functions.php";

$a = checkLogin(); if($a==1) {
$id =$_COOKIE['id'];

include "databaseConnector.php";

$query =$mysqli->query("SELECT * FROM users WHERE id = '$id'") or die($mysqli->error.__LINE__);

if($query->num_rows > 0) { while($row = $query->fetch_assoc()) { ?> <?php echo stripslashes($row['firstname'])." ".stripslashes($row['lastname']); ?> <?php } } else { return false; } } else { redirectIndex(); } ?>  - ("SELECT * FROM users WHERE id = '$id'") - read about SQL injection! – Peter Kiss Mar 7 '13 at 19:57