How do you program a custom WordPress plug-in?

Question

I have seen several WordPress plug-ins for adding a "quote of the day" feature (or something similar) to your blog.

How do you create a customized one? I'm looking for something that will pull a daily entry from a list/database of my creation.

I apologize if my question is not detailed enough. Still a newbie with WordPress.

PART 2: Thanks for your prompt and on-point responses. With your responses and some additional research, I'm able to fine-tune my question. What I wish to accomplish is something similar to Amazon's Deal of the Day widget. Except, in my case, it will simply be a title and a corresponding link.

My presumption is that I will set up a database and (using php or something similar) have the information drawn from the database and displayed in my WP sidebar.

Additionally, I forgot to mention the time element. I want the displayed info to update once a day, at or around the same time each day.

Any ideas?

Thanks again. I'm so glad I found stackoverflow.

Answer 1

Please see Writing a Plugin:

WordPress Plugins allow easy modification, customization, and enhancement to a WordPress blog. Instead of changing the core programming of WordPress, you can add functionality with WordPress Plugins.

Also, WP Tutorial: Your First WP Plugin might interest you as well:

Here it is, a video guide to creating your first WordPress plugin (in under 5 minutes!). If people like this enough, I might do these kinds of tutorials on a regular basis.

Answer 2

For anything beyond basic looks (i.e. HTML/CSS twiddling), you'll have to know PHP. Start with the links posted by Andrew Hare, but basically Wordpress provides the user with "hooks" into its system. Hooks can be used by catching various events (e.g. "I'm going to display the post summary") and modifying them before they reach the user.

A good idea would be to find some plugin that does something similar to what you want and look at its code. All plugins are open-source - you can download their source code and look at the .php files yourself.