add_meta_box( string $id, string $title, callable $callback, string|array|WP_Screen $screen = null, string $context = 'advanced', string $priority = 'default', array $callback_args = null )

向一个或多个屏幕添加元框。
Adds a meta box to one or more screens.

参数（Parameters）

返回（Return）

源码（Source）

/**
 * Add a meta box to an edit form.
 *
 * @since 2.5.0
 *
 * @global array $wp_meta_boxes
 *
 * @param string           $id            String for use in the 'id' attribute of tags.
 * @param string           $title         Title of the meta box.
 * @param callback         $callback      Function that fills the box with the desired content.
 *                                        The function should echo its output.
 * @param string|WP_Screen $screen        Optional. The screen on which to show the box (like a post
 *                                        type, 'link', or 'comment'). Default is the current screen.
 * @param string           $context       Optional. The context within the screen where the boxes
 *                                        should display. Available contexts vary from screen to
 *                                        screen. Post edit screen contexts include 'normal', 'side',
 *                                        and 'advanced'. Comments screen contexts include 'normal'
 *                                        and 'side'. Menus meta boxes (accordion sections) all use
 *                                        the 'side' context. Global default is 'advanced'.
 * @param string           $priority      Optional. The priority within the context where the boxes
 *                                        should show ('high', 'low'). Default 'default'.
 * @param array            $callback_args Optional. Data that should be set as the $args property
 *                                        of the box array (which is the second parameter passed
 *                                        to your callback). Default null.
 */
function add_meta_box( $id, $title, $callback, $screen = null, $context = 'advanced', $priority = 'default', $callback_args = null ) {
	global $wp_meta_boxes;

	if ( empty( $screen ) )
		$screen = get_current_screen();
	elseif ( is_string( $screen ) )
		$screen = convert_to_screen( $screen );

	$page = $screen->id;

	if ( !isset($wp_meta_boxes) )
		$wp_meta_boxes = array();
	if ( !isset($wp_meta_boxes[$page]) )
		$wp_meta_boxes[$page] = array();
	if ( !isset($wp_meta_boxes[$page][$context]) )
		$wp_meta_boxes[$page][$context] = array();

	foreach ( array_keys($wp_meta_boxes[$page]) as $a_context ) {
		foreach ( array('high', 'core', 'default', 'low') as $a_priority ) {
			if ( !isset($wp_meta_boxes[$page][$a_context][$a_priority][$id]) )
				continue;

			// If a core box was previously added or removed by a plugin, don't add.
			if ( 'core' == $priority ) {
				// If core box previously deleted, don't add
				if ( false === $wp_meta_boxes[$page][$a_context][$a_priority][$id] )
					return;

				/*
				 * If box was added with default priority, give it core priority to
				 * maintain sort order.
				 */
				if ( 'default' == $a_priority ) {
					$wp_meta_boxes[$page][$a_context]['core'][$id] = $wp_meta_boxes[$page][$a_context]['default'][$id];
					unset($wp_meta_boxes[$page][$a_context]['default'][$id]);
				}
				return;
			}
			// If no priority given and id already present, use existing priority.
			if ( empty($priority) ) {
				$priority = $a_priority;
			/*
			 * Else, if we're adding to the sorted priority, we don't know the title
			 * or callback. Grab them from the previously added context/priority.
			 */
			} elseif ( 'sorted' == $priority ) {
				$title = $wp_meta_boxes[$page][$a_context][$a_priority][$id]['title'];
				$callback = $wp_meta_boxes[$page][$a_context][$a_priority][$id]['callback'];
				$callback_args = $wp_meta_boxes[$page][$a_context][$a_priority][$id]['args'];
			}
			// An id can be in only one priority and one context.
			if ( $priority != $a_priority || $context != $a_context )
				unset($wp_meta_boxes[$page][$a_context][$a_priority][$id]);
		}
	}

	if ( empty($priority) )
		$priority = 'low';

	if ( !isset($wp_meta_boxes[$page][$context][$priority]) )
		$wp_meta_boxes[$page][$context][$priority] = array();

	$wp_meta_boxes[$page][$context][$priority][$id] = array('id' => $id, 'title' => $title, 'callback' => $callback, 'args' => $callback_args);
}