I'm trying to determine the best way to expand on WP.
I love the base of WP for a website... it has pretty much everything needed for a website.
But now and again I need to be able to create some custom "pages" or small apps within the WP framework. For example, I've created a small app within a sub-directory of my WP install (/cart) for a purchase form. I'm including the WP head for access to the WP methods, but I don't feel that this is the most effective way of extending WP.
I've also looked into integrating other PHP frameworks like CodeIgniter and Yii ... again, I'm not sure this is the best approach.
Is there a way to create a WP plugin that has it's own "directory" or path? http://mywpinstall.com/customapp/
WP has so many great things going for it, that I'd love to be able to expand on it without touching the core.
Thanks in advance.