add_action in wordpress

add_action( string $tag, callable $function_to_add, int $priority = 10,int $accepted_args = 1 )

Description

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

Parameters

$tag: (string) (Required) The name of the action to which the $function_to_add is hooked.

$function_to_add (callable) (Required) The name of the function you wish to be called.

$priority (int) (Optional) Used to specify the order in which the functions associated with a particular action are executed. Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the action.

Default value: 10 $accepted_args (int) (Optional) The number of arguments the function accepts.

Default value: 1

Example:

Add action hook function is used to execute our custom function without disturbing the core functionality of wordpress.

add_action('wp_enqueue_scripts','custom_scripts');
function custom_scripts()
{
 wp_register_style('my-custom-css', plugins_url('css/my_css.css', __FILE__));
 wp_enqueue_style('my-custom-css');
 wp_enqueue_script( 'my-custom-js', plugins_url( '/js/my_js.js', __FILE__ ), array('jquery') );
}

when custom_scripts function is executes then it adds my custom css style and js script to the header part in front end.