wp_count_posts( string $type = 'post', string $perm = '' )

统计一个帖子类型的帖子数以及用户是否有查看权限。
Count number of posts of a post type and if user has permissions to view.

说明（Description）

此函数提供了一种有效的方法来查找blog的类型。另一种方法是计算get_posts（）中的项数，但该方法的开销很大。因此，在为2.5+开发时，请改用此函数。$perm参数检查“readable”值，如果用户可以读取私有帖子，它将为登录的用户显示该值。

参数（Parameters）

源码（Source）

/**
 * Count number of posts of a post type and if user has permissions to view.
 *
 * This function provides an efficient method of finding the amount of post's
 * type a blog has. Another method is to count the amount of items in
 * get_posts(), but that method has a lot of overhead with doing so. Therefore,
 * when developing for 2.5+, use this function instead.
 *
 * The $perm parameter checks for 'readable' value and if the user can read
 * private posts, it will display that for the user that is signed in.
 *
 * @since 2.5.0
 *
 * @global wpdb $wpdb
 *
 * @param string $type Optional. Post type to retrieve count. Default 'post'.
 * @param string $perm Optional. 'readable' or empty. Default empty.
 * @return object Number of posts for each status.
 */
function wp_count_posts( $type = 'post', $perm = '' ) {
	global $wpdb;

	if ( ! post_type_exists( $type ) )
		return new stdClass;

	$cache_key = _count_posts_cache_key( $type, $perm );

	$counts = wp_cache_get( $cache_key, 'counts' );
	if ( false !== $counts ) {
		/** This filter is documented in wp-includes/post.php */
		return apply_filters( 'wp_count_posts', $counts, $type, $perm );
	}

	$query = "SELECT post_status, COUNT( * ) AS num_posts FROM {$wpdb->posts} WHERE post_type = %s";
	if ( 'readable' == $perm && is_user_logged_in() ) {
		$post_type_object = get_post_type_object($type);
		if ( ! current_user_can( $post_type_object->cap->read_private_posts ) ) {
			$query .= $wpdb->prepare( " AND (post_status != 'private' OR ( post_author = %d AND post_status = 'private' ))",
				get_current_user_id()
			);
		}
	}
	$query .= ' GROUP BY post_status';

	$results = (array) $wpdb->get_results( $wpdb->prepare( $query, $type ), ARRAY_A );
	$counts = array_fill_keys( get_post_stati(), 0 );

	foreach ( $results as $row ) {
		$counts[ $row['post_status'] ] = $row['num_posts'];
	}

	$counts = (object) $counts;
	wp_cache_set( $cache_key, $counts, 'counts' );

	/**
	 * Modify returned post counts by status for the current post type.
	 *
	 * @since 3.7.0
	 *
	 * @param object $counts An object containing the current post_type's post
	 *                       counts by status.
	 * @param string $type   Post type.
	 * @param string $perm   The permission to determine if the posts are 'readable'
	 *                       by the current user.
	 */
	return apply_filters( 'wp_count_posts', $counts, $type, $perm );
}

笔记（Notes）