The MenuService technique...

MenuService.php

<?php

namespace DeltaX\Crud\MenuService;

/**
 * Use to process input from Query Strings
 * or HTTP Request bodies. Process Data determines
 * if it'll a last step.
 *
 */

abstract class MenuService {

	/**
	 * Response: The Status Code
	 * 
	 * @var int
	 */
	protected $code = 0;

	/**
	 * Response: The main content 
	 * of the response body
	 * 
	 * @var mixed
	 */
	protected $outputData;


	/**
	 * The data to be processed
	 * 
	 * @var array
	 */
	protected $inputData = [];

	/**
	 * The constructor
	 * 
	 * @param array $input
	 * @return void 
	 */
	public function __construct(array $input = []){

		if (! empty($input)) {
			$this->inputData = $input;	
		}	
	}


	/**
	 * Accept an array of instances of 
	 * MenuService. Each will process their
	 * input data then return their output 
	 * data so the next instance can use 
	 * the output data as their input data. 
	 * When there is no instance left in 
	 * the array, the last one shall be returned
	 * 
	 * @return self
	 */
	public function prepend(self ...$menuServices){

		$remainingMenuSvcs = $menuServices;
		$currentMenuSvc = array_shift($remainingMenuSvcs);

		//Prepare and "prepend" the remaining MenuServices
		if ( $currentMenuSvc && $this->code === 0 ) {

			$currentMenuSvc = $currentMenuSvc->setInputData($this->inputData);
			$currentMenuSvc = $currentMenuSvc->setCode($this->code);

			$msData = $currentMenuSvc->processData()->prepareResponse();
			
			$this->code = $msData['code'];
			$this->inputData = $msData['data'];

			return $this->prepend(...$remainingMenuSvcs);	
		}

		$this->outputData = $this->inputData;
		return $this;	
		
	}


	/**
	 * Set the input.
	 * Prefereably called upon __construct()
	 * 
	 * @param array $input
	 * @return self
	 */
	public function setInputData(array $input) {
		$this->inputData = $input;
		return $this;
	}

	/**
	 * Set the code. 
	 * Preferrably, only to be used by
	 * prepend()
	 * 
	 * @param int $status
	 * @return self
	 */
	public function setCode(int $status) {
		$this->code = $status;
		return $this;
	}
	
	/**
	 * Response: prepare the response body.
	 * 
	 * @return array
	 */
	public function prepareResponse() {
		return [
			'code' => $this->code,
			'data' => $this->outputData
		];
	}

	/**
	 * Let the $inputData be processed by the
	 * prepended MenuServices
	 * 
	 * @param  self $menuServices,...
	 * @return self
	 */
	public function execute(self ...$menuServices){

		if ( ! empty($menuServices) ) {
			$prepended = $this->prepend( ...$menuServices )->prepareResponse();
			$this->inputData = $prepended['data'];
			$this->code = $prepended['code'];
		}
		
		if ($this->code === 0) {
			$this->processData();
		}

		return $this;
	}

	/**
	 * Process data: implement this method  to use the 
	 * $inputData to your will. This must also modify the
	 * $outputData and $code depending on the circumstance.
	 * 
	 * @return self
	 */
	abstract protected function processData();

}

A MenuService can be treated as a step of an HTTP Request-Response transaction.

Usually, when accessing a set of grades in school, there are these questions and happenings. The assumed input is a Query String converted in an associative array.

1. The raw array shall be converted into a SearchFilter (always return a code 0)
2. "Are you allowed to access this?" (If no, return a code 401, 0 if yes)
3. "Is your input valid for this?"(If no, return with a code 400, 0 if yes)
4. Fetch Data (return with a code 200)

Using prepend(), all steps will be done through processData() of objects of MenuService class. Should a MenuService change the $code through the series, It'll end with that MenuService that changed the $code from 0 to whatever.

To translate into code...

public function getChecklist($request, $response, $arguments){

		$input = $request->getQueryParams();
		$input['student_number'] = $request
			->getAttribute('route')
			->getArgument('student_number');

                $userIdentity = (new StudentIdentity(
			new SentinelAuthenticationAdapter($this->app->sentinel), 
			new CentralRepository))->setIdentityKey($input['student_number']);

		/*** The Main MenuService */
                $studentChecklistSvc = (new MultipleReadService($input))
			->setModelService(new StudentChecklist(new CentralRepository));

                /*** The Prepended MenuServices */
                $searchFilterSvc = new SearchFilterService();

                $authService = new AuthorizationService($userIdentity, ['admin']);
	
		$validatorSvc = new SearchValidatorService(new ChecklistSearchValidation);
		
                /*** THIS IS THE EXAMPLE */
		$output = $studentChecklistSvc
			->execute($searchFilterSvc, $authService, $validatorSvc)
			->prepareResponse();

		return $response->withJson($output['data'], $output['code']);
}