If you want to seperate PHP-code from HTML-code, you need some kind of template system. vlibTemplate provides such a system. This is a detailed german guide for vlibTemplate. It contains 3 examples for simlple templates and 3 examples for loops/blocks.
Friendly URL's are a very important thing to have when developing a dymanic content site that uses long query strings. A query string is something similiar to a URL like you'll see on Ebay, Google and other big sites. If you're running a small to medium size website and you want to make your URL's a little easier to find you can do so via Apache's mod_rewrite by following this tutorial.
When you write a PHP script and want to distribute it, it must still fall under some legal terms. The GNU GPL is the best method to get your work out into the world, and of course as open source software.
COM allows the reuse of code written in any language. This tutorial explains how to read records from ms-access database through php. COM functions are only available on the Windows version of php. In order to run this script you should have com.allow_dcom has to be set to true in php.ini.
Search engine Web spiders, however, tend to ignore pages whose URL contains GET method parameters. This article explains how to use your Web server to pass parameters to PHP scripts so that it fools search engines, and allows your page to be indexed when it would otherwise be ignored.