Quick and dirty illustration of my comment to MKStandard on reddit. I know this could be improved - especially as the BaseRepository is assuming it uses Eloquent models (maybe an AbstractRepository that gets extended by an EloquentBaseRepository would be another logical layer of abstraction?) - but I think this should be enough of an illustratio…

gistfile1.php

<?php

class BaseRepository {

  /**
  * our model instance
  *
  * @var $model
  */
  protected $model = null;
  
  /**
  * get our model
  *
  * @return $model
  */
  protected function getModel()
  {
    return $this->model;
  }
  
  /**
  * set our model
  *
  * @return void
  */
  protected function setModel($model)
  {
    $this->model = $model;
  }
  
  public function get($id, array $related = null)
  {
    if(is_array($id))
    {
      $results = $this->model->whereIn("id", $id)->get();
    }
    else
    {
      $results = $this->model->findOrFail($id);
    }
  
    if( ! is_null($related))
    {
      $results->load($related);
    }
  
    return $results;
  }
}

class EloquentMeasurementRepository extends BaseRepository implements MeasurementRepositoryInterface
{
  public function __construct(Measurement $model)
  {
    $this->setModel($model);
  }
}

You might also want to wrap the interior of the get function in an if (!is_null($this->model)){ ... } or similar to prevent trying to use null as a model. Like I said, quick and dirty.

Accessor or Mutators should be public or removed. In the constructor for EloquentMeasurementRepository you can set the model like this: $this->model = $model.

This also works but that's not what accessor and mutators are meant for.