Question

What is the best way to “NOT” display a page directly in php?

Edit

There is a page = register.php
a user cant open register.php directly. Only can access from index.php > Register.php
Thanks

Answer 1

Any PHP files containing sensitive data, such as database password, should be stored outside of the document root and included where needed. That way, if an admin makes a serious mistake and the web server starts sending PHP unparsed, that data will be inaccessible.

Edit

You edited your question and it now seems you wish to prevent access to page without them coming from a particular page. You should be able to get some ideas from these questions:

deny direct access to a php file by typing the link in the url

preventing direct access to a php page, only access if redirected