Core_Command::_multisite_convert PHP Method

    private function _multisite_convert($assoc_args)
    {
        global $wpdb;
        require_once ABSPATH . 'wp-admin/includes/upgrade.php';
        $domain = self::get_clean_basedomain();
        if ('localhost' === $domain && !empty($assoc_args['subdomains'])) {
            WP_CLI::error("Multisite with subdomains cannot be configured when domain is 'localhost'.");
        }
        // need to register the multisite tables manually for some reason
        foreach ($wpdb->tables('ms_global') as $table => $prefixed_table) {
            $wpdb->{$table} = $prefixed_table;
        }
        install_network();
        $result = populate_network($assoc_args['site_id'], $domain, get_option('admin_email'), $assoc_args['title'], $assoc_args['base'], $assoc_args['subdomains']);
        if (true === $result) {
            WP_CLI::log('Set up multisite database tables.');
        } else {
            if (is_wp_error($result)) {
                switch ($result->get_error_code()) {
                    case 'siteid_exists':
                        WP_CLI::log($result->get_error_message());
                        return false;
                    case 'no_wildcard_dns':
                        WP_CLI::warning(__('Wildcard DNS may not be configured correctly.'));
                        break;
                    default:
                        WP_CLI::error($result);
                }
            }
        }
        // delete_site_option() cleans the alloptions cache to prevent dupe option
        delete_site_option('upload_space_check_disabled');
        update_site_option('upload_space_check_disabled', 1);
        if (!is_multisite()) {
            $subdomain_export = Utils\get_flag_value($assoc_args, 'subdomains') ? 'true' : 'false';
            $ms_config = <<<EOT
define( 'WP_ALLOW_MULTISITE', true );
define( 'MULTISITE', true );
define( 'SUBDOMAIN_INSTALL', {$subdomain_export} );
\$base = '{$assoc_args['base']}';
define( 'DOMAIN_CURRENT_SITE', '{$domain}' );
define( 'PATH_CURRENT_SITE', '{$assoc_args['base']}' );
define( 'SITE_ID_CURRENT_SITE', 1 );
define( 'BLOG_ID_CURRENT_SITE', 1 );
EOT;
            $wp_config_path = Utils\locate_wp_config();
            if (is_writable($wp_config_path) && self::modify_wp_config($ms_config)) {
                WP_CLI::log("Added multisite constants to 'wp-config.php'.");
            } else {
                WP_CLI::warning("Multisite constants could not be written to 'wp-config.php'. You may need to add them manually:" . PHP_EOL . $ms_config);
            }
        }
        return true;
    }