Illuminate\Database\Eloquent\Model::getOriginal PHP Method

    public function getOriginal($key = null, $default = null)
    {
        return Arr::get($this->original, $key, $default);
    }

 /**
  * Update the cache for all operations.
  *
  * @param Model $model
  */
 public function updateCache(Model $model)
 {
     $this->model = $model;
     $this->applyToCountCache(function ($config) {
         $foreignKey = $this->key($this->model, $config['foreignKey']);
         if ($this->model->getOriginal($foreignKey) && $this->model->{$foreignKey} != $this->model->getOriginal($foreignKey)) {
             $this->update($config, '-', $this->model->getOriginal($foreignKey));
             $this->update($config, '+', $this->model->{$foreignKey});
         }
     });
 }