WordPress® All-in-One For Dummies®

Making Your Plugin Pluggable

The WordPress API provides a great solution for hooking in and extending or modifying its functionality. Sometimes, however, you may find that it would be useful to hook into another plugin, rather than WordPress itself, and extend or modify its functionality instead.

Here's an example of making your plugin pluggable: an issue about interaction (or lack of) between WP e-Commerce (http://getshopped.org) and the All in One SEO Pack plugin. All in One SEO Pack, among other things, adds a custom document title, description, keywords, and canonical URL to each page on a WordPress site. People often ask how to have their plugin modify this information before it displays onscreen. Forum plugins and shopping cart plugins particularly have this need, which All in One SEO Pack could easily satisfy if it would just provide a method of accessing its functionality, which it has — read on.

WP e-Commerce (and other plugins with similar functionality) creates its own virtual pages for product listings, and so on, all contained on a single WordPress page. For example, if you define http://mywebstore.com/shop as the WordPress page WP e-Commerce uses, http://mywebsite.com/shop/product-name and all other product pages are dynamically created by the WP e-Commerce plugin, and are outside the reach of other WordPress plugins. So, WordPress, and by extension, the All in One SEO Pack plugin, doesn't know about them. You can see the problem this would create for SEO purposes; ...