An laravel's style implementation of API handler.

ApiController.php

<?php
/*************************************************
 * API base controller for laravel
 *************************************************/
class ApiController extends Controller {

	/**
	 * Create a json Response including errors and no data
	 * @param  array  $errors the errors
	 * @return responce        The responce including error data
	 */
	private function jsonError(array $errors)
	{
		return $this->jsonReply(array(), $errors);
	}

	/**
	 * Create a json Response, including data and errors
	 * @param  array  $data   The data
	 * @param  array  $errors The errors
	 * @return Responce	The responce containing json encoded data
	 */
	private function jsonReply(array $data, array $errors = array())
	{
		if(!empty($errors))
		{	
			//Crée le contenant
			if(!isset($data['errors']))
			{
				$data['errors'] = new MessageBag();
			}
			
			if(!($data['errors'] instanceof MessageBag))
			{
				throw new Exception('errors element in json must be a MessageBag instance');
			}
		
			//ajoute les erreurs au contenant actuel
			if ($errors instanceof MessageProviderInterface)
			{
				$data['errors']->merge($errors->getMessageBag()->toArray());
			}
			else
			{
				$data['errors']->merge((array) $errors);
			}
			
			//converti en array pour le transfert en json si la collection n'est pas vide, détruit sinon
			if($data['errors']->any())
				$data['errors'] = $data['errors']->toArray();
			else
				unset($data['errors']);

			//erreur, defini le success a false
			$data['success'] = false;
		}
	
		//retourne la reponse contenant les données et le json
		return Response::json($data);
	}

	/**
	 * Execute the passed function then return the result (or exceptions) as json
	 * @param  Closure $f The function to execute
	 * @return string     data as json encoded string
	 */
	public function apiOutput(Closure $f)
	{
		try
		{
			$default['success'] = true;
			$return = $f();
			$return = array_merge($default, (array) $return);

			return $this->jsonReply($return);
		}
		catch (AppException $e)
		{
			$return['exception'] = $e->getMessage();

			return $this->jsonError($return);
		}
		catch (Exception $e)
		{
			$return['exception'] = $e->getMessage();

			Log::error($e->__toString());
			return $this->jsonError($return);
		}
	}

}

/*************************************************
 * Usage example (API side)
 *************************************************/
class TestAPI extends ApiController {

	function index()
	{
		return $this->apiOutput(function(){
			if(!Auth::check()) 
			{
				//exceptions are returned in JSON in the form :
				//{success:false, exception: "Exception message"}
				throw new AppException('errors.mustlogin');
			}

			//prepare some random data
			$view_data = array();
			$view_data['var1'] = 17;
			$view_data['var2'] = "SomeTest";
			$view_data['var3'] = Auth::user()->toArray();
			
			//the view data is translated into json form
			//Resulting output is in the form:
			//{success:true, var1:17, var2:"SomeTest", var3:{UserAsJson}}
			return $view_data;
		});
	}

}

/*************************************************
 * Non API base controller for laravel
 *************************************************/
class BaseController extends Controller {
	
	/**
	 * Call an internal api url
	 *
	 * @return \StdClass response
	 */
	protected function callApi($url, $method = 'GET', $input = null)
	{
		Profiler::startTimer('Api call to '.$url);
		
		if(is_null($input))
		{
			$input = Request::input();
		}
	
		//save original input
		$originalInput = Request::input();
		Request::replace($input);
		
		//dispatch the request, then parse the responce
		$request = Request::create($url, $method);
		$responce = json_decode(Route::dispatch($request)->getContent());
		
		//get error array from JSON (if any)
		if(isset($responce->errors) && !empty($responce->errors))
		{
			$data = App::make('view')->getShared();
			if(isset($data['errors']))
			{
				$data['errors']->merge((array) $responce->errors);
			}
			else
			{
				$data['errors'] = new MessageBag((array) $responce->errors);
			}
			
			App::make('view')->share('errors', $data['errors']);
		}
		
		//Replace original input
		Request::replace($originalInput);
		
		Profiler::endTimer('Api call to '.$url);
		
		return $responce;
	}

}

/*************************************************
 * Non API controller (frontend) Usage example
 *************************************************/
class TestFrontend extends BaseController {

	public function index()
	{
		//just in case?
		if(!Auth::check()) 
		{
			return Redirect::to(action('Home@index'));
		}
		
		$view_data = array();
		
		$responce = $this->callApi('/api/test');
		if ($view_data['success'] == 1) 
		{
			$view_data['var1'] = $responce->var1;
			$view_data['var2'] = $responce->var2;
			$view_data['var3'] = $responce->var3;
			return View::make('testapi', $view_data);
		} 
		else 
		{
			//Display error using message in $responce['exception']
			return View::make('errorpage', $responce);
		}
	}
}