Check if username already are registrated to table

Question

I need help checking if a usersname already are registrated or exist in the table. I tried alot but it seems that it just letting it true.

my codes are:

//=============Configuring Server and Database=======
$host        =    'localhost';
$user        =    'root';
$password    =    '';
//=============Data Base Information=================
$database    =    'login';

$conn        =    mysql_connect($host,$user,$password) or die('Server Information is not               Correct'); //Establish Connection with Server
mysql_select_db($database,$conn) or die('Database Information is not correct');

//===============End Server Configuration============

//=============Starting Registration Script==========

$username    =    mysql_real_escape_string($_POST['username']);

$password    =    mysql_real_escape_string($_POST['password']);

$email    =    mysql_real_escape_string($_POST['email']);

$country    =    mysql_real_escape_string($_POST['country']);



if(isset($_POST['btnRegister'])) //===When I will Set the Button to 1 or Press Button to  register
{
$query    =    "insert into     users(username,password,email,country)values('$username','$password','$email','$country')" or    die ('username allready exist');
$res    =    mysql_query($query);
header("location:load.php");

Answer 1

Replace:

$query    =    "insert into     users(username,password,email,country)values('$username','$password','$email','$country')" or    die ('username allready exist');
$res    =    mysql_query($query);

With:

$query    =    "insert into     users(username,password,email,country)values('$username','$password','$email','$country')" ;
$res    =    mysql_query($query) or    die ('username allready exist');

The problem with your original code is that you are checking that the $query variable is correctly instantiated (and I see no reason why it wouldn't). You need to check if the query was successfully executed or not, i.e. to check the result of the query call (mysql_query in your case).

Note that your production code shouldn't be using the mysql_* functions (which are not good practice) and should use prepared statements. See here: [http://uk1.php.net/manual/en/function.mysql-query.php][1]

Please, don't use mysql_* functions in new code. They are no longer maintained and are officially deprecated. See the red box? Learn about prepared statements instead, and use PDO, or MySQLi - this article will help you decide which. If you choose PDO, here is a good tutorial.