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   global $CACHE_MANAGER, $XXX;

   function getKey($key, $level = 0)
   {
      $dir = '/tagdirx/' .substr(md5($key),2,2).'/'.$key.'/';   // Правильный вариант

      $cache = Bitrix\Main\Data\Cache::createInstance();
      if ($cache->initCache(200, $key, $dir))
      {
         $var = $cache->getVars();
      }
      else
      {
         $taggedCache = \Bitrix\Main\Application::getInstance()->getTaggedCache();
         $taggedCache->StartTagCache($dir);
         $taggedCache->RegisterTag($key);
         $cache->startDataCache();
         $taggedCache->EndTagCache();
         $cache->endDataCache(['time_bx_test' => getmicrotime()]);
         $var['time_bx_test'] = "Empty cache";
      }

      return $key.":".$var['time_bx_test'];
   }


   $taggedCache = \Bitrix\Main\Application::getInstance()->getTaggedCache();

global $cacheLog;
$cacheLog = true;


   $XXX = true;
   for ($i = 0; $i < 4; $i++)
   {
      echo getKey("K{$i}")."\n";
   }

 $taggedCache->ClearByTag('K0'); echo "\n\n\n";
$taggedCache->ClearByTag('K2'); echo "\n\n\n";

   for ($i = 0; $i < 4; $i++)
   {
      echo getKey("K{$i}")."\n";
   }