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

将函数挂接到特定操作上。
Hooks a function on to a specific action.

目录锚点：#说明#参数#返回#源码#笔记

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说明（Description）

Actions是WordPress核心在执行期间或发生特定事件时在特定点启动的钩子。插件可以使用Action API指定在这些点上执行一个或多个PHP函数。

参数（Parameters）

返回（Return）

（true）将始终返回true。

源码（Source）

/**
 * Hooks a function on to a specific action.
 *
 * 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   $tag             The name of the action to which the $function_to_add is hooked.
 * @param callback $function_to_add The name of the function you wish to be called.
 * @param int      $priority        Optional. Used to specify the order in which the functions
 *                                  associated with a particular action are executed. Default 10.
 *                                  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.
 * @param int      $accepted_args   Optional. The number of arguments the function accepts. Default 1.
 * @return true Will always return true.
 */
function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
	return add_filter($tag, $function_to_add, $priority, $accepted_args);
}

笔记（Notes）

与类一起使用
与类中的静态函数一起使用
简单挂钩