Generally a word Hooks Stands for Lines or lines written to entice a reader or listener to learn more. This is an introduction that will grab people’s attention.
Hooks in wordpress, Hooks are a way for one code to communicate/change another code in specific, predefined locations. They form the basis for how plug-ins and themes interact with the WordPress core, but they are widely used by the core.
Actually they are classified into two types of hooks: Actions and filters.
Working with hooks on WordPress starts with figuring out what you need to link your code to, then write the code to execute the data you need or any action you need.
In WordPress theme and development, hooks are functions that can be used in an action or WordPress filter. Actions and filters in WordPress are functions that can be changed by the theme and plugin developers to change the functionality of the default WordPress.
Functions used to change actions/filters in WordPress can be integrated with WordPress.
However, it should be noted that actions and filters are not the same thing. Functions performed when a specific event occurs in WordPress are called Actions. Filter allows you to change certain functions. The arguments used to combine both filters and actions are identical. But they differ in functions and in behaviours.
An example of a hook used as a filter in WordPress
function wpb_custom_excerpt( $output ) {
if ( has_excerpt() && ! is_attachment() ) {
$output .= wpb_continue_reading_link();
}
return $output;
}
add_filter( ‘get_the_excerpt’, ‘wpb_custom_excerpt’ );
The sample code above creates a function wpb_custom_excerpt which is hooked into get_the_excerpt filter.
An example of a hook used for action
function mytheme_enqueue_script() {
wp_enqueue_script( ‘my-custom-js’, ‘custom.js’, false );
}
add_action( ‘wp_enqueue_scripts’, ‘mytheme_enqueue_script’ );
The sample code above creates a function mytheme_enqueue_script which is hooked into wp_enqueue_scripts action.
Actions and filters are the two types of filters which you need to write a custom function called a callback, and then for a specific action or filter register with a WordPress hook.
Actions allow you to add data or change how WordPress works. Callback functions for Actions run at a certain point in WordPress implementation, and the user can perform some sort of task, such as echoing the output or inserting something into the database. Actions do not return anything to the calling hook.
Filters give you the ability to transfer data when WordPress is activated. Withdrawal(callback) functions for filters accept a variable, modify it, and return. They should operate in isolation and should never cause side effects such as global variables and affecting output. Filters expect something to come back to them.
WordPress provides many hooks that you can use, but you can also create your own so that other developers can extend and modify your plugin or theme.
Many hooks that are offered by the WordPress which you can use, you can also create your own. It helps developers to extend and modify your plugin or theme.
Actions against filters
The main difference between an action and a filter can be summarized as follows
An action takes the information it receives and does something with it, not returning anything. In other words: it works on something and then exits, and nothing returns to the call hook.
A filter takes the information it receives, modifies it, and returns it. In other words it filters something and sends it back to the hook for further use.
Another way said:
An action prevents code flow to do something, and then returns to normal flow without changing anything;
A filter is used to change something in a certain way, so the change is then used by the index.
The one specified is the list of parameters sent via the hook definition. More about this in later sections.
Simple steps to add and remove your own functions
If you want to combine your own functions, the process is very simple. You need to know some information first. For actions, you need to know the name of the hook and when it will run. For filters, you also need to know the name of the hook, but you also need to know what value you are going to get and what you want to get back. The name of the process that contains all the information you need and all your codes.
How to Hook into an Action
add_action( $hook, $function_to_add, $priority, $accepted_args );
The required parameters of the add_action function are the hook and function to add. The priority is an optional integer value based on a scale of 1 to 999 that determines the priority of order for functions tied to that specific hook. Higher priority means it runs later, lower priority means earlier. The last parameter is used less often and it is for when you need to pass or accept multiple arguments.
How to Hook into an Filter
add_filter( $tag, $function_to_add, $priority, $accepted_args );
Add_filter works just like add_action. You have to be careful, because sometimes a hook is both an action and a filter, or a filter and a function. You will find a real difference with the actual function you call.
Note that for a filter, both function_to_add receive a value and must return it at the end of the process. Actions, on the other hand, run the code they need and do not give value.
How to Unhook from Actions and Filters
A hook is very easy to remove. Use the remove_action or remove_filter function with the name of the hook, function and preference. If you want to unpack a function that has been linked more than once, it is preferably optional and helpful if you only want to delete a specific instance of that function.
remove_action( $tag, $function_to_remove, $priority );
remove_filter( $tag, $function_to_remove, $priority );
We have now looked at the basics of how functions are hooked and unhooked
