add_action() – Adds a callback function to an action hook.

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Adds a callback function to an action hook.

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.


$true = add_action( $hook_name, $callback, $priority, $accepted_args );


( string ) required – The name of the action to add the callback to.
( callable ) required – The callback to be run when the action is called.
( int ) optional default: 10 – 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 10.
( int ) optional default: 1 – Optional. The number of arguments the function accepts. Default 1.


true Always returns true.


File name: wordpress/wp-includes/plugin.php

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function add_action( $hook_name, $callback, $priority = 10, $accepted_args = 1 ) {
  return add_filter( $hook_name, $callback, $priority, $accepted_args );

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