Source

File: wp-includes/class-wp-network-query.php

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

		/**
		 * Fires before networks are retrieved.
		 *
		 * @since 4.6.0
		 *
		 * @param WP_Network_Query $this Current instance of WP_Network_Query (passed by reference).
		 */
		do_action_ref_array( 'pre_get_networks', array( &$this ) );

		$network_data = null;

		/**
		 * Filter the network data before the query takes place.
		 *
		 * Return a non-null value to bypass WordPress's default network queries.
		 *
		 * The expected return type from this filter depends on the value passed in the request query_vars.
		 * When `$this->query_vars['count']` is set, the filter should return the network count as an int.
		 * When `'ids' === $this->query_vars['fields']`, the filter should return an array of network IDs.
		 * Otherwise the filter should return an array of WP_Network objects.
		 *
		 * @since 5.2.0
		 *
		 * @param array|null       $network_data Return an array of network data to short-circuit WP's network query,
		 *                                       the network count as an integer if `$this->query_vars['count']` is set,
		 *                                       or null to allow WP to run its normal queries.
		 * @param WP_Network_Query $this         The WP_Network_Query instance, passed by reference.
		 */
		$network_data = apply_filters_ref_array( 'networks_pre_query', array( $network_data, &$this ) );

		if ( null !== $network_data ) {
			return $network_data;
		}

		// $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( 'networks' );

		$cache_key   = "get_network_ids:$key:$last_changed";
		$cache_value = wp_cache_get( $cache_key, 'networks' );

		if ( false === $cache_value ) {
			$network_ids = $this->get_network_ids();
			if ( $network_ids ) {
				$this->set_found_networks();
			}

			$cache_value = array(
				'network_ids'    => $network_ids,
				'found_networks' => $this->found_networks,
			);
			wp_cache_add( $cache_key, $cache_value, 'networks' );
		} else {
			$network_ids          = $cache_value['network_ids'];
			$this->found_networks = $cache_value['found_networks'];
		}

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

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

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

		if ( 'ids' === $this->query_vars['fields'] ) {
			$this->networks = $network_ids;
			return $this->networks;
		}

		if ( $this->query_vars['update_network_cache'] ) {
			_prime_network_caches( $network_ids );
		}

		// Fetch full network objects from the primed cache.
		$_networks = array();
		foreach ( $network_ids as $network_id ) {
			$_network = get_network( $network_id );
			if ( $_network ) {
				$_networks[] = $_network;
			}
		}

		/**
		 * Filters the network query results.
		 *
		 * @since 4.6.0
		 *
		 * @param WP_Network[]     $_networks An array of WP_Network objects.
		 * @param WP_Network_Query $this      Current instance of WP_Network_Query (passed by reference).
		 */
		$_networks = apply_filters_ref_array( 'the_networks', array( $_networks, &$this ) );

		// Convert to WP_Network instances.
		$this->networks = array_map( 'get_network', $_networks );

		return $this->networks;
	}