Professional WordPress Plugin Development, 2nd Edition

5Hooks

WHAT'S IN THIS CHAPTER?

• Creating actions for action hooks
• Creating filters for filter hooks
• Using hooks with PHP classes and anonymous functions
• Creating custom hooks in plugins
• Finding hooks within WordPress

CODE DOWNLOADS FOR THIS CHAPTER

The code downloads for this chapter are found at www.wiley.com/go/prowordpressdev2e on the Downloads tab.

Hooks are the “bread and butter” of WordPress. They're the essential feature you need to build plugins. Hooks allow plugins to plug in to WordPress and “do stuff.” While it is possible to build a plugin that doesn't rely on the hooks system, such plugins would be a rarity. The majority of plugins will use at least one hook.

Once you start learning how hooks work, you will begin understanding why WordPress is such a powerful platform. It has allowed a community of thousands of developers to build upon it for years, which has in turn propelled the software's growth beyond systems without any easy way for third‐party developers to build upon them.

UNDERSTANDING HOOKS

In WordPress, hooks are the primary feature of the Plugin API. They enable plugin developers to “hook” into the WordPress flow and alter how it works without modifying the core code. By not altering core WordPress, users can upgrade to newer versions without losing any modifications that their plugins have done.

Plugins would have no way to modify how WordPress works without hooks. In many ways, hooks represent what plugins are. The lessons you learn ...