does .php files need the .php extension?

From Hiding PHP on PHP.net:

Another tactic is to configure web servers such as apache to parse different filetypes through PHP, either with an .htaccess directive, or in the apache configuration file itself. You can then use misleading file extensions:

# Make PHP code look like unknown types
AddType application/x-httpd-php .bop .foo .133t

---

So you can add a .htaccess rule that would mean that your server treats .tpl, .dlf etc as if they were PHP files, like so:

AddType application/x-httpd-php .tpl .dlf .dbh

---

However, if you are just using include or require, it doesn't matter what extension you use:

include "inc/template.tpl";
require "inc/database.dbh";
require_once("inc/config.ext.php.url.tpl.cfg");

You can change server config to enterpret other file extensions as PHP

In Apache you can add to this:

<FilesMatch \.php$>
SetHandler application/x-httpd-php
</FilesMatch>

if you include the files, then any extension will do:

in script.php:

include 'includes/foo.inc';
include 'inlcudes/bar.whatever';

will all work