function getDataCache()
 {
     $file = fopen("data.txt", "r");
     while (!feof($file)) {
         $line = fgets($file);
         $part = explode(":", $line);
         if ($part[0] == $this->city) {
             $timestamp = time() - $part[2];
             $minutes = $timestamp / 600;
             if ($minutes < 10) {
                 $this->temperature = $part[1];
                 $this->isInCache = true;
             }
         }
     }
     if (!$this->isInCache) {
         parent::getData();
         $file = fopen("data.txt", "a");
         $line = $this->city . ':' . $this->temperature . ':' . time() . "\r\n";
         fwrite($file, $line);
     }
 }