WordPress Hooks are functions that theme and plugin developers use to modify Actions or Filters to change the default functionality. Action and Filter functions can be ‘hooked’ into WordPress to achieve this. WordPress provides many hooks, but you can create your own to let other developers modify or expand your theme or plugin.
What are Actions and Filters?
Actions and Filters are two hook variations that seem the same but are not identical regarding behavior and functionality. For example, actions are done when a specific event occurs in WordPress. Filters, on the other hand, allow certain functions to be altered.
Hooks enable a piece of code to modify or interact with another code at precise, pre-defined spots. They are the basis for how themes and plugins interact with WordPress’s Core but are also used extensively by Core itself.
How to Use Action & Filter Hooks?
To use Filter or Action hooks required writing a “Callback” custom function and then registering it with a WordPress hook for a specific filter or action.
Actions let you add data or change how WordPress functions. Actions run at a specific point when implementing WordPress Core, themes, and plugins. Action Callback functions can, for example, insert something into the database or repeat output to the user. These Callback functions do not return anything to the calling Action hook.
Filters allow you to change data while executing WordPress Core, themes, and plugins. Filter Callbacks accept a variable, alter it, and return it. Filters are supposed to work in isolation and with no side effects like changing global variables and output. Additionally, Filters expect something to be returned.
In simpler terms
WordPress sums up the main difference between a filter and action as follows:
- A filter takes the info it receives, modifies it somehow, and returns it. In other words: it filters something and passes it back to the hook for further use.
- An action takes the info it receives, does something with it, and returns nothing. In other words: it acts on something and then exits, returning nothing to the calling hook.
In other words:
- A filter modifies something in a specific way so that the modification is then used by code later on.
- An action interrupts the code flow to do something and then returns to the normal flow without modifying anything.