PHP Include

I am creating a site where most of my pages will be password protected, and those pages will not be viewable unless a customer has purchased a membership and signed up using their email and creating a password. In order to allow thousands of people access to password protected pages while using a password and username they created (thousands of people with thousands of different passwords), we wanted to add the following php include:

<?php
include(“/home/public_html/checkuser.php”);
?>

I was wondering if there would be any issues if i were to put this on every page I want password protected. Maybe it would not work or affect the functionality of the pages. Any help would be appreciated.

Thanks,
Max