|Filename||Hook Type||Line Number||PHP Doc|
* 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.
* @since 1.2.0
* @param string $hook_name The name of the action to add the callback to.
* @param callable $callback The callback to be run when the action is called.
* @param int $priority 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.
* @param int $accepted_args Optional. The number of arguments the function accepts. Default 1.
* @return true Always returns true.