function username_exists($username){
global $db;
$sql = "SELECT 'username' FROM users WHERE 'username' = '$username'";
$result = mysqli_query($db, $sql);
confirmquery( $result );
if (mysqli_num_rows($result) > 0) {
return true;
}else {
return false;
}
}
if(username_exists($username)){
$error['username'] = 'Username already exists';
}