In the end, I got this function. I don’t know whether it’s normal or not.
function user_registration($user_name, $user_email, $user_pass, $address,
$city, $postalcode, $country, $phone, $mobilephone)
How and why can I improve this?
You could either pass an array with all variables packed nicely together, or just make a “User” class and add all properties via setters and do the validation in the end with a dedicated method: