How to display login/register errors?

1. How to show login error message in PHP?
2. What is registration and login called?

How to show login error message in PHP?

The quickest way to display all php errors and warnings is to add these lines to your PHP code file: ini_set('display_errors', 1); ini_set('display_startup_errors', 1); error_reporting(E_ALL);

What is registration and login called?

entry. as an appropriate name for a single form for both login and registration. The name makes it clear it's the entry point.