add_action()添加动作

<?php wp_head();?>

/**
 * 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      $accepted_args   Optional. The number of arguments the function accept. Default 1.
 * @return bool Will always return true.
 */
function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
	return add_filter($tag, $function_to_add, $priority, $accepted_args);
}

function test_add_action() {
    echo '<meta name="keywords" content="关于我们" />';
}
add_action( 'wp_head', 'test_add_action' );