Simple started class for the wp api, requires https://wordpress.org/plugins/rest-api/

WP_API_Starter_WP

<?php
/**
 * @package WordPress
 * @subpackage ProjectName
 * @license GPL v2 - http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 *
 * Description:
 **/
####################################################################################################



/**
 * WP_API_Starter_WP
 * @since 1.0
 **/
new WP_API_Starter_WP();
class WP_API_Starter_WP extends WP_REST_Controller {

	/**
	 * version
	 *
	 * @access public
	 * @var int
	 * @since 1.0
	 **/
	public $version = 1;

	/**
	 * namespace
	 *
	 * @access public
	 * @var string
	 * @since 1.0
	 **/
	public $namespace = 'vendor';



	/**
	 * __construct
	 **/
	function __construct() {

		add_action( 'rest_api_init', array( $this, 'register_routes' ) );

	} // end function __construct



	####################################################################################################
	/**
	 * Set Get
	 **/
	####################################################################################################



	/**
	 * set
	 * @since 1.0
	 **/
	function set( $key, $val = false ) {

		if ( isset( $key ) AND ! empty( $key ) ) {
			$this->$key = $val;
		}

	} // end function set



	/**
	 * get
	 * @since 1.0
	 **/
	function get( $key ) {

		if ( isset( $key ) AND ! empty( $key ) AND isset( $this->$key ) AND ! empty( $this->$key ) ) {
			return $this->$key;
		} else {
			return false;
		}

	} // end function get



	/**
	 * get_route
	 * @since 1.0
	 **/
	function get_route( $route ) {

		return '/v' . $this->get('version') . '/' . $route;

	} // end function get_route



	####################################################################################################
	/**
	 * Functionality
	 **/
	####################################################################################################



	/**
	 * Register the routes for the objects of the controller.
	 */
	public function register_routes() {
		register_rest_route( $this->get('namespace'), $this->get_route( 'route/test' ), array(
			array(
				'methods' => WP_REST_Server::READABLE,
				'callback' => array( $this, 'testing_function' ),
				'permission_callback' => '__return_true',
				'args' => array()
			)
		) );
	}



	/**
	 * Testing
	 *
	 * @param WP_REST_Request $request Full data about the request.
	 * @return WP_Error|WP_REST_Response
	 */
	public function testing_function( $request ) {

		$data = $this->prepare_response_for_collection( array( 'data' => array( 'data', 'data', 'data' ) ) );

		if ( $data ) {
			return new WP_REST_Response( $data, 200 );
		} else {
			return new WP_Error( 'no data', __( 'message', 'text-domain'), array( 'status' => 500 ) );
		}
	}



} // end class WP_API_Starter_WP