The below query is always returning an empty array i have checked that the $_POST is working but i am unsure what is going on?
$database = new wpdb(QLBBackendUser, QLBBackendPass, QLBBackendDB, DB_HOST);
if (isset($_POST['register-user'])):
$user = $database->get_results('SELECT * FROM users WHERE email='.$_POST["user_email"]);
var_dump($user);
endif;
Please note this is for Wordpress using WPDB Class.
You should never call the wpdb class directly...If you must, use the global $wpdb object instead. In addition, make sure the user_email has been POSTed (I'm not sure why you're checking for register-user being set and not user_email). Also, it's highly unlikely that the table you should be querying is called users (without a prefix). It's likely wp_users if you're using the default prefix.
Finally, there is a handy function that already does what you're trying to re-implement, called get_user_by:
$user = get_user_by( 'email', $_POST['user_email'] );
I recommend using the above, instead of trying to re-invent the wheel.
$wpdb->get_results( $wpdb->prepare( "SELECT * FROM {$wpdb->users} WHERE email=%s", $_POST['user_email'] ) );. I believe it's important to point out the security hole that they had in their original query(using $_POST directly), even if it doesn't serve them now it is an important lesson to learn.
$wpdb object directly...however, it is unsafe to pass $_POST data directly to $wpdb. Instead you should sanitize this data, before passing it to $wpdb. And yes, using functions like get_user_by() is the way to do it withough $wpdb
wpdbclass directly...Use the global$wpdbobject instead...Read more in the codex