Basic Information of WordPress

History

WordPress was created by Matt Mullenweg and Mike Little in 2003. It was initially developed as a fork of an existing blogging software called b2/cafelog. Over the years, it has evolved into a comprehensive CMS and has become the most popular platform for building websites.

WordPress Action

In WordPress, an action refers to a specific event or hook that is triggered at a certain point during the execution of a WordPress page or process. Actions are an essential part of the WordPress plugin and theme development architecture, allowing developers to extend or modify the default functionality of WordPress.

When an action is triggered, it executes a set of functions or code snippets that are associated with that particular action. These functions can perform various tasks such as modifying data, adding content, registering hooks, enqueueing scripts or styles, and more.

Actions are typically defined using the add_action() function, which takes two main parameters: the name of the action and the function to be executed when the action is triggered. Developers can also pass additional parameters to the function using the third parameter of add_action().

For example, the following code adds an action called ‘init’ that executes the ‘my_custom_function’ function when the ‘init’ action is triggered:

function my_custom_function() {
// Code to be executed when the action is triggered
// …
}
add_action(‘init’, ‘my_custom_function’);

In this example, whenever the ‘init’ action is fired during the WordPress initialization process, the ‘my_custom_function’ function will be called.

Actions provide a way to modify and extend the behavior of WordPress without directly modifying the core code. They allow developers to hook into specific points in the execution flow of WordPress and add their own custom functionality, making WordPress highly customizable and adaptable to various requirements.

WordPress Hook

In WordPress, a hook refers to a predefined location or point in the execution flow of a WordPress page or process where developers can attach their custom functions or code snippets. Hooks enable developers to modify or extend the default behavior of WordPress without directly modifying the core files.

There are two types of hooks in WordPress:

1. Action Hooks: Action hooks allow developers to execute their custom code at specific points in the execution flow. When an action hook is encountered, all functions attached to that hook are executed. Actions are typically used to perform tasks such as adding content, modifying data, registering hooks, enqueueing scripts or styles, and more. Examples of action hooks include “init,” “wp_enqueue_scripts,” and “template_redirect.”

2. Filter Hooks: Filter hooks provide a way to modify or filter data before it is displayed or used by WordPress. When a filter hook is encountered, the data passed to that hook can be modified by functions attached to the hook. Filters are used to manipulate content, modify query results, modify URLs, and more. Examples of filter hooks include “the_content,” “the_title,” and “wp_nav_menu_items.”

Hooks are defined using the `add_action()` and `add_filter()` functions. Developers can attach their custom functions to hooks using these functions, specifying the hook name and the function to be executed.

For example, the following code attaches a custom function to the “the_content” filter hook to modify the content before it is displayed:

function my_custom_function($content) {
// Modify the content
$modified_content = $content . ‘ Additional content added.’;
return $modified_content;
}
add_filter(‘the_content’, ‘my_custom_function’);

In this example, the “my_custom_function” function is attached to the “the_content” filter hook. When the “the_content” hook is encountered, the “my_custom_function” function is called, and the content is modified before being displayed.

Hooks form the foundation of the WordPress plugin and theme development architecture, allowing developers to customize and extend WordPress functionality in a modular and flexible way. They provide a means to hook into different points of the execution flow, making WordPress highly customizable and adaptable to specific needs.

Difference between Action and Filter in WordPress

In WordPress, both actions and filters are hooks that allow developers to modify or extend the functionality of WordPress. While they are similar in concept, there are some key differences between actions and filters:

1. Purpose: Actions are primarily used to perform tasks or actions at specific points in the execution flow of WordPress. They allow developers to add or execute their custom code at specific events, such as when a page is loaded, a post is saved, or a plugin is activated. Actions are typically used to add content, modify data, register hooks, enqueue scripts or styles, and more.

Filters, on the other hand, are used to modify or filter data before it is displayed or used by WordPress. They allow developers to modify the value of a variable, content, or settings by passing it through one or more functions attached to the filter. Filters are commonly used to manipulate content, modify query results, modify URLs, and customize various aspects of WordPress.

2. Execution: Actions are executed by calling the `do_action()` function at the specific point in the code where the action is intended to occur. When an action is triggered, all functions attached to that action are executed in the order they were added.

Filters, on the other hand, are executed by calling the `apply_filters()` function when the filter is encountered. The value passed through the filter is modified by functions attached to that filter, and the modified value is returned.

3. Return Value: Actions do not expect or return any value. They are meant to perform actions or tasks without modifying the data being processed.

Filters, on the other hand, expect a value to be passed through them and usually modify that value before returning it. The modified value can then be used by WordPress or other functions that rely on that filtered data.

4. Hook Functions: Actions are registered using the `add_action()` function, which specifies the action name and the function to be executed when the action occurs.

Filters are registered using the `add_filter()` function, which also specifies the filter name and the function to be executed. However, filter functions are expected to receive a value, modify it if needed, and return the modified value.

Here’s an example to illustrate the difference:

// Action example
function my_custom_action_function() {
// Perform an action or task
}
add_action (‘my_custom_action’, ‘my_custom_action_function’);

// Filter example
function my_custom_filter_function($value) {
// Modify the value and return it
$modified_value = $value . ‘ Modified’;
return $modified_value;
}
add_filter (‘my_custom_filter’, ‘my_custom_filter_function’);

In the example, the action `my_custom_action` is registered to execute the function `my_custom_action_function` when triggered. On the other hand, the filter `my_custom_filter` is registered to execute the function `my_custom_filter_function`, which modifies the value passed through the filter and returns the modified value.

In summary, actions are used to perform actions or tasks at specific points, while filters are used to modify or filter data. Actions do not expect or return values, while filters expect a value, modify it, and return the modified value. Both actions and filters provide flexibility and extensibility in customizing WordPress functionality.

WordPress API

The WordPress API (Application Programming Interface) refers to a set of rules and protocols that allow different software applications to interact with and communicate with WordPress. It provides a standardized way for developers to access and manipulate WordPress data and functionality.

WordPress offers several APIs that serve different purposes:

REST API: The WordPress REST API is the most commonly used API in WordPress. It allows developers to retrieve and manipulate WordPress data using HTTP requests. The REST API provides endpoints for posts, pages, users, comments, media, taxonomies, and more. It enables developers to create, read, update, and delete WordPress content programmatically, making it easier to build applications that interact with WordPress.

XML-RPC API: The XML-RPC API enables remote communication with a WordPress site. It allows external applications to perform various actions on a WordPress site, such as creating and editing posts, managing comments, and retrieving user information. While the XML-RPC API is older and less commonly used than the REST API, it still provides a way for legacy systems or older applications to interact with WordPress.

Admin Ajax API: The Admin Ajax API is specific to the WordPress administration interface. It allows developers to create Ajax-powered features within the WordPress dashboard. With the Admin Ajax API, developers can send requests to the server and receive responses without refreshing the entire page. This API is often used to enhance the user experience by providing interactive elements and dynamic content in the WordPress admin area.

Plugin and Theme APIs: WordPress also provides APIs specifically designed for plugin and theme developers. These APIs offer functions and hooks that allow developers to extend WordPress functionality, modify the behavior of themes and plugins, add custom settings and options, and integrate with various parts of the WordPress ecosystem. Examples include the Plugin API for developing WordPress plugins and the Theme Customization API for adding customizable options to themes.

The WordPress API enables developers to integrate WordPress with external applications, create custom applications, extend WordPress functionality, and automate tasks. It provides a structured and documented way to interact with WordPress, making it easier to build powerful and customized solutions on top of the WordPress platform.