public static function prepareUpload()
 {
     include_once ABSPATH . '/wp-admin/includes/plugin-install.php';
     $output = array();
     $output['sites'] = array();
     if ($_POST['selected_by'] == 'site') {
         //Get sites
         foreach ($_POST['selected_sites'] as $enc_id) {
             $websiteid = $enc_id;
             if (MainWP_Utility::ctype_digit($websiteid)) {
                 $website = MainWP_DB::Instance()->getWebsiteById($websiteid);
                 $output['sites'][$website->id] = MainWP_Utility::mapSite($website, array('id', 'url', 'name'));
             }
         }
     } else {
         //Get sites from group
         foreach ($_POST['selected_groups'] as $enc_id) {
             $groupid = $enc_id;
             if (MainWP_Utility::ctype_digit($groupid)) {
                 $websites = MainWP_DB::Instance()->query(MainWP_DB::Instance()->getSQLWebsitesByGroupId($groupid));
                 while ($websites && ($website = @MainWP_DB::fetch_object($websites))) {
                     if ($website->sync_errors != '') {
                         continue;
                     }
                     $output['sites'][$website->id] = MainWP_Utility::mapSite($website, array('id', 'url', 'name'));
                 }
                 @MainWP_DB::free_result($websites);
             }
         }
     }
     $output['urls'] = array();
     foreach ($_POST['files'] as $file) {
         $output['urls'][] = MainWP_Utility::getDownloadUrl('bulk', $file);
     }
     $output['urls'] = implode('||', $output['urls']);
     $output['urls'] = apply_filters('mainwp_installbulk_prepareupload', $output['urls']);
     die(json_encode($output));
 }