code: public function increment($field, $step = 1)
      {
          $int = $this->get($field);
          if (is_numeric($int)) {
              $int += $step;
              $this->set($field, $int);
  
              return $int;
          }
  
          return null;
      }
docs: @param int|string $field Selected field in which the value will be incremented.
  @param int|float  $step  Incrementation step.
  
  @return int|float|null Returns the new value or null if the value on $field is not numeric.