Hello, for some reason everytime I register on my website, I get "Could not check username" no matter what I use. I'm sure it might be a spelling mistake(?) but I've looked through everywhere and couldn't find it.

Here's my snippet:

Code:
if(isset($_POST['username'])){ }
	
	$username = $_POST['username'];

$username = preg_replace("#[^0-9a-z]#i","",$username);
...