Explain add_action() function in wordpress.

The add_action() function in WordPress is a crucial part of the WordPress Plugin API. It allows you to add custom functionality to your WordPress site. Here's a step-by-step explanation of how it works:

1. Understanding Hooks: Before understanding add_action(), you need to understand the concept of Hooks. Hooks in WordPress allow you to change or add code without editing core files. They are used to make your plugins and themes compatible with future updates.

2. Action Hooks: Action Hooks are the hooks that WordPress core launches at specific points during execution, or when specific events occur. Your plugin can specify that one or more of its PHP functions are executed at these points, using the Action API.

3. Using add_action(): The add_action() function is used to attach those functions to the action hooks. It tells WordPress when to execute a function.

4. Syntax: The basic syntax of add_action() function in WordPress is: add_action( $hook, $function_to_add, $priority, $accepted_args );

   • $hook (required): The name of the action to which the $function_to_add is hooked.
   • $function_to_add (required): The name of the function you wish to be called.
   • $priority (optional): Used to specify the order in which the functions associated with a particular action are executed. Lower numbers correspond with earlier execution. If not set, default is 10.
   • $accepted_args (optional): The number of arguments the function accepts. If not set, default is 1.

5. Example: Here's a simple example of how to use add_action() function:

function custom_function() {
    // Your code here.
}
add_action('wp_footer', 'custom_function');

In this example, 'custom_function' will be executed when the 'wp_footer' action is triggered.