I am building a new site which will consist of a mix of dynamic and static pages.

I would like to add commenting functionality to those pages with as little work as possible. I'm curious as to whether such a solution exists in PHP.

The ideal set of features would be:

• Completely independent from the surrounding page / site: PHP code gets dropped into page, a page ID is added, done.
• Simple "write a comment" form
• Comments for each page are displayed using a PHP function
• Nice, clean output of <ul><li>.... that can be styled by the surrounding site
• Optional Captcha
• Optional Gravatar sensitivity
• Minimalistic administration area to moderate/delete comments, no ACL, can protect it using .htaccess

The ideal integreation would be like this:

<?php show_comments("my_page_name"); ?>

this would 1. display a form to add a new comment that gets automatically associtated with my_page_name; and 2. display all comments that were made through this form using this ID.

Does anybody know a solution like this?

Bounty

I am setting up a bounty because while there were some good suggestions, they all point to external services. I'm really curious to see whether there isn't anything self-hosted around. If this doesn't exist yet, it sure would be great to see as an Open Source project.