code: protected function generateIntersection($combinationMask) {
      $combination = [];
      foreach (str_split($combinationMask) as $key => $indicator) {
        if ($indicator) {
          $combination[] = $this->arrays[$this->arrayKeys[$key]];
        }
      }
      $intersection = call_user_func_array('array_intersect_assoc', $combination);
      if (count($intersection) >= $this->threshold) {
        $this->intersections[] = $intersection;
        return;
      }
      $this->noResultMasks[] = $combinationMask;
    }
docs: Generate intersections based on a combination mask.
  
  @param string $combinationMask
  The combination mask to try.