Wordpress basic concept - how to extend/override/customize a plugin hook?

Question

I am working on a wordpress site and would like to clarify a basic concept that is definitely very important, and this is how to customize/extend a wordpress hook (at least that's what I think I want to do!)

As the real world example, I am setting up a wp-ecommerce site. When a user adds an item to the cart, I would like to do one or two more things than the original function does. Looking through the source, I find:

/wp-content/plugins/wp-e-commerce/wpsc-includes/ajax.functions.php

with the function:

function wpsc_add_to_cart()

I know I could simply edit the code right here, but obviously that is the completely wrong way to go about it as when the plugin is updated, I will lose changes. What is the correct way to extend a function that is part of a plugin, or wordpress for that matter?

Endless thanks in advance.

Answer 1

You can use the wordpress action hooks to resolve the code loss while plugin upgrade.

You can remove the function which is in plugin file by using remove_action hook and do your own code by adding add_action in your function.php file. So that you can customize your plugin code from theme's function.php.

Here are the examples to explain.I hope it will help.

http://codex.wordpress.org/Plugin_API

http://themeshaper.com/2009/05/03/filters-wordpress-child-themes/