code: private function getIssetInfo(Tokens $tokens, $index)
      {
          $openIndex = $tokens->getNextMeaningfulToken($index);
  
          $braceOpenCount = 1;
          $meaningfulTokenIndexes = [$openIndex];
  
          for ($i = $openIndex + 1;; ++$i) {
              if ($tokens[$i]->isWhitespace() || $tokens[$i]->isComment()) {
                  continue;
              }
  
              $meaningfulTokenIndexes[] = $i;
  
              if ($tokens[$i]->equals(')')) {
                  --$braceOpenCount;
                  if (0 === $braceOpenCount) {
                      break;
                  }
              } elseif ($tokens[$i]->equals('(')) {
                  ++$braceOpenCount;
              }
          }
  
          return $meaningfulTokenIndexes;
      }
docs: @param Tokens $tokens
  @param int    $index  of T_ISSET
  
  @return int[] indexes of meaningful tokens belonging to the isset statement