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Must-Know Differences Between WordPress Actions And Filters

Post by|WordPress13 October,2020
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In the earlier days of my professional life, when I just began with WordPress as my choice of technology, I heard my seniors and colleagues using certain words called “HOOK,” “ACTION,” “FILTER.” However, at that time, I could not understand these words well.

Initially, I was able to apply these actions and filters in separate files based on the WordPress theme; however, I could not understand it well, but over time when I began working on WordPress very closely, I understood these words.

I believe that budding WordPress developers might be facing similar issues with action and filters. Therefore, I have written this blog to ease their dilemma and clarify these critical aspects as WordPress developers.

Most interviewers ask for the differences between action and filters while recruiting. So, you could benefit here in multiple ways.

I have tried to explain this difference in my words and based on my understanding. I hope you guys will like it.

Note: To extend WordPress’s functionality, we use the WordPress Provided Plugin API, which is two Core Elements, Actions, and Filters, and these Actions and Filters are called Actions Hook or Filter Hook. Although both are conceptually quite different, the practical implementation of these two is almost the same. So the hook covers both the part action and filter; however, both are slightly different from each other. I have explained it in more detail below.

What Are Action Hooks?

WordPress provides us different hooks. Using those hooks, we can efficiently execute our codes while WordPress core code executes.

It means that WordPress provides us with a Hook System, using which we can return the content that is returning as a response during the WordPress Initialization Process itself. We can change according to our needs or in the event of a specific event, i.e., in the event of a particular Action being executed, we can run a function code of our own that can meet the specific Type requirement.

The first thing is to run any of the actions. It must have the do_action() in the files. Without the do_action function, you will not add any action in the themes’ function file. do_action() has the parameter which is like below example:

do_action( ‘example_action_to_run’, $arg1, $arg2 );

Here, the example_action will be your action, and the argument you have passed you can access when you add the functions.php file.

The do_action will be majorly declared in the WordPress or WordPress plugins’ core files. As a good WordPress developer, you need to use that action rather than modifying the file directly. Let’s see how you can activate the above do_action()

// The action callback function.
function example_callback_fun( $arg1, $arg2 ) {
You can access the $arg1 here and $arg2 here. You just need to manipulate it and check the output.
}
add_action( ‘example_action_to_run’, ‘example_callback_fun’, 10, 2 );

Let me tell you all the parameters; however, it is not connected to the action and filter difference, but it is a fundamental concept which any WordPress developer needs to understand.

In the above add_action, the first parameter is the action name, the second parameter is the function name, and the third is based on the priority of the function that will run. Hence, if your priority is higher, it will run in the end. The fourth parameter is the argument. If you pass one, then you will not be able to access the second argument.

Hence, you need to check how many parameters are there in the do_action. Based on it, you can set the limit of the parameter.

There is no limitation in using the action. You can use much time, but it is based on prioritizing the last priority for the output.

What Are Filters Hooks?

Using filter hooks, we can modify content that returns while WordPress responds. Content means the text of a page or post, or author name, or any options which retrieve from the database.

Filters are functions that always accept data in the form of an Argument and, after processing again, return the data as Return Value.

The filter itself means the process of filtering something out. So, when I say that I want to filter salt from the bucket of water, the meaning is implied. So action executes something to get the results while the filter allows you to filter the data from system generated output.

Just like the do_action, here we have the apply_filters() function. If someone has not mentioned the apply_filters() in the code you must not be able to use the filter it will surely throw the error while running the page. Let’s check more in little details with examples just like the action.

$filtered_value = apply_filters( example_filter_to_run, ‘filter me’, $arg1, $arg2 );

So, now the $filtered_value will be the system generated output until you add a filter on it. In order, add the filter you need to call add_filter() just like the add_action(). Below is the example :

// The filter callback function based on the filter.
function example_callback_fun( $string, $arg1, $arg2 ) {
// (maybe) modify $string.
return $string;
}
add_filter( ‘example_filter_to_run’, ‘example_callback_fun’, 10, 3 );

Here the parameter concept remains the same, just like the add_action() function. First is the filtername. The second parameter is the function name, the third is the priority, and there the fourth is augment. Also, there is no limitation to apply filters but based on the priority; it will give the results.

Note: You need to give the return value once you modify it.

Distinguishing Differences Between Action Hooks & Filters Hooks

The primary difference between Actions Hook and Filters Hook is that Actions Hook is always rough. WordPress Action means Execute in Response to WordPress Event and does not require any type of data compulsory. Whereas Filters Hook still needs data.

Actions can have any functionality, and Filters can exist to modify data.

Actions may or may not passed any data by their action hook, and Filters are passed data to modify by their hook.

Actions do not return their changes, and Filters must return their changes.
Actions hooked in via add_action() and Filters hooked in via add_filters()

Here are some Actions Functions listed:

  • has_action()
  • do_action()
  • add_action()
  • remove_action() etc..

Here are some Filters Functions listed:

  • has_filter()
  • doing_filter()
  • add_filter()
  • remove_filter() etc..

We can categorize different Action Hooks in WordPress into different categories as follows:

  • Post, Page, Attachment, and Category actions
  • Comment. Ping and trackback actions,
  • Blogroll actions
  • Feed actions
  • Template actions
  • Administrative actions
  • Advanced actions

We can categorize different Filter Hooks in WordPress into different categories as follows:

  • Category and terms filters
  • Link filters
  • Date and Time filters
  • Author and User filters
  • Blogroll filters
  • Blog information and options filters
  • Administrative filters
  • Template filters
  • Login and Registration filters
  • Redirect/Rewrite filters
  • WP_query filters
  • Widget filters
  • Advanced WordPress filters

Conclusion

The primary use for this hook is that you do not need to change the core files or anything; you can have the default file as it so the WordPress community can handle their core files and release the update. They provide all significant hooks in the right place, which are more than enough to achieve your project requirements.

In conclusion, the hooks make the WordPress developer’s life easy and allow you to extend any project or task’s functionality. It is allowing you to modify the content. Simultaneously, it will enable you to change the default WordPress action.

Now, I understand that sometimes, you need a helping hand to walk you through the process. At ZealousWeb, you not only get one helping hand but plenty. You can either hire a WordPress developer or an entire team to cater to your customized needs.

FAQ

Is it mandatory to give the do_action() and do_filter() in wordpress plugin development?

No, it is not mandatory, but if you give the action and filter, developers will surely recommend your plugin as they are getting the flexibility to extend your plugin results.

Is it mandatory to return the function in the add_filter()?

Yes, indeed, you required the add_filter function; otherwise, the code will not understand what changes need to apply to it.

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