WP_Site_Query::get_sites()

	public function get_sites() {
		$this->parse_query();

		/**
		 * Fires before sites are retrieved.
		 *
		 * @since WP-4.6.0
		 *
		 * @param WP_Site_Query $this Current instance of WP_Site_Query (passed by reference).
		 */
		do_action_ref_array( 'pre_get_sites', array( &$this ) );

		// $args can include anything. Only use the args defined in the query_var_defaults to compute the key.
		$_args = wp_array_slice_assoc( $this->query_vars, array_keys( $this->query_var_defaults ) );

		// Ignore the $fields argument as the queried result will be the same regardless.
		unset( $_args['fields'] );

		$key = md5( serialize( $_args ) );
		$last_changed = wp_cache_get_last_changed( 'sites' );

		$cache_key = "get_sites:$key:$last_changed";
		$cache_value = wp_cache_get( $cache_key, 'sites' );

		if ( false === $cache_value ) {
			$site_ids = $this->get_site_ids();
			if ( $site_ids ) {
				$this->set_found_sites();
			}

			$cache_value = array(
				'site_ids' => $site_ids,
				'found_sites' => $this->found_sites,
			);
			wp_cache_add( $cache_key, $cache_value, 'sites' );
		} else {
			$site_ids = $cache_value['site_ids'];
			$this->found_sites = $cache_value['found_sites'];
		}

		if ( $this->found_sites && $this->query_vars['number'] ) {
			$this->max_num_pages = ceil( $this->found_sites / $this->query_vars['number'] );
		}

		// If querying for a count only, there's nothing more to do.
		if ( $this->query_vars['count'] ) {
			// $site_ids is actually a count in this case.
			return intval( $site_ids );
		}

		$site_ids = array_map( 'intval', $site_ids );

		if ( 'ids' == $this->query_vars['fields'] ) {
			$this->sites = $site_ids;

			return $this->sites;
		}

		// Prime site network caches.
		if ( $this->query_vars['update_site_cache'] ) {
			_prime_site_caches( $site_ids );
		}

		// Fetch full site objects from the primed cache.
		$_sites = array();
		foreach ( $site_ids as $site_id ) {
			if ( $_site = get_site( $site_id ) ) {
				$_sites[] = $_site;
			}
		}

		/**
		 * Filters the site query results.
		 *
		 * @since WP-4.6.0
		 *
		 * @param array         $_sites An array of WP_Site objects.
		 * @param WP_Site_Query $this   Current instance of WP_Site_Query (passed by reference).
		 */
		$_sites = apply_filters_ref_array( 'the_sites', array( $_sites, &$this ) );

		// Convert to WP_Site instances.
		$this->sites = array_map( 'get_site', $_sites );

		return $this->sites;
	}