question is why ?
why should otjher pages process a page ?
and with 'process' do you mean that it should redirect user to that page
or
stay on this page and only include the work that is done in the other page ?
it is common to use small resourse pages, that contains some function
that many pages can use
than these functions in include pages can easily be incorporated wherever needed
<?php // this is: firstpage.php
include ( "somefunctions1.php" );
include ( "otherfunctions2.php" );
?>
Hello world!<br>
<a href="nextpage.php">LINK go to next page</a>