Source

File: wp-includes/post.php

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 ) {
		// We may have cached this before every status was registered.
		foreach ( get_post_stati() as $status ) {
			if ( ! isset( $counts->{$status} ) ) {
				$counts->{$status} = 0;
			}
		}

		/** 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 );
}