<?php

namespace app\controllers;

use Yii;
use yii\filters\AccessControl;
use yii\web\Controller;
use yii\filters\VerbFilter;
use yii\helpers\Json;

use app\models\WhiteBoard;

class ApiwhiteboardController extends Controller{
	
	public function beforeAction($action) {
	    $this->enableCsrfValidation = false;
	    return parent::beforeAction($action);
	}

	function respondJSONCode($pCode){
		$msg = "Unknown Error.";
		switch($pCode){
			case 400: $msg = "Bad request";break;
			case 404: $msg = "The requested element was not found.";break;
			case 200: $msg = "Ok.";break;
			case 406: $msg = "Not Acceptable.";break;
		}
		return $this->respondJSON(null,$pCode,$msg);
	}

	function respondJSON($responseValue=null,$code=200,$msg="Ok"){
		Yii::$app->response->format = \yii\web\Response::FORMAT_JSON;
		$headers = Yii::$app->response->headers;
        $headers->add('Content-Type', 'application/json');
        
        $responseObject = array('code'=>$code,'value'=>$responseValue);
        
        if($responseValue == null){
        	$responseObject['msg'] = $msg;
        }

        return $responseObject;
        Yii::$app->end();
    }
    
    function actionAll() {
        $messages = WhiteBoard::find()->all();
        
        return $this->respondJSON(self::model2Array( $messages ) );
    }

	/**
	*View a single element
	*/
	public function actionView($id){
		$m = WhiteBoard::findOne($id);
        
		if($m == null){
			return $this->respondJSONCode(404);
		}else{
			return $this->respondJSON( self::model2Array( $m ) );	
		}
	}

    
    /**
    *Delete element by id
    */
    public function actionDelete($id){
        $m = WhiteBoard::findOne($id);
        if($m == null){
			return $this->respondJSONCode(404);
		}else{
            if($m->delete())
			    return $this->respondJSON( );
            else
                return $this->respondJSON( array('action'=>'delete', 'status'=>'error', 'errors'=>$m->errors) );	
		}
    }
    
    /**
    *Create element by raw json
    */
    public function actionCreate(){
        $json = file_get_contents('php://input');
        $put_vars = Json::decode($json,true);  //true means use associative array
        
        if(empty($put_vars))
        {
            return $this->respondJSON( array('error'=>'Bad request', 'expected'=>'json raw data'), 400 );
            Yii::$app->end();
        }
        
        $m = new WhiteBoard;
        $m->attributes = $put_vars;
        
        if($m->save())
            return $this->respondJSON( array('action'=>'create', 'status'=>'ok', 'attributes'=>$m->attributes) );
        else
            return $this->respondJSON( array('action'=>'create', 'status'=>'error', 'attributes'=>$m->attributes, 'errors'=>$m->errors) );    
    }
    
    /**
    *Update element by raw json
    *TODO: determinar si hace falta retornar los atributos, al menos el ID de la insersion ese si
    */
    public function actionUpdate($id){
        $json = file_get_contents('php://input');
        $put_vars = Json::decode($json,true);  //true means use associative array
        
        if(empty($put_vars))
        {
            return $this->respondJSONCode( 400 );
            Yii::$app->end();
        }
        
        $m = WhiteBoard::findOne($id);
        if($m == null) {
            return $this->respondJSONCode( 404 );
            Yii::$app->end();
        }
        
        $m->attributes = $put_vars;
        if($m->save())
            return $this->respondJSON( array('action'=>'update', 'status'=>'ok', 'attributes'=>$m->attributes) );
        else
            return $this->respondJSON( array('action'=>'update', 'status'=>'error', 'attributes'=>$m->attributes, 'errors'=>$m->errors) );    
    }
    
    //Util func
	private static function model2Array($models) {
        if (is_array($models))
            $arrayMode = TRUE;
        else {
            $models = array($models);
            $arrayMode = FALSE;
        }

        $result = array();
        foreach ($models as $model) {
            $attributes = $model->getAttributes();
            
            if ($arrayMode)
                array_push($result, $attributes);
            else
                $result = $attributes;
        }
        return $result;
    }
	
}
?>

Yii2 API Example, desde cero

Controllador

$config = [

     ...

    'components' => [
         'urlManager' => [
                'class' => 'yii\web\UrlManager',
                // Disable index.php
                'showScriptName' => false,
                // Disable r= routes
                'enablePrettyUrl' => true,
                'rules' => [
                        'GET api/whiteboard/'=>'apiwhiteboard/all',
                        'GET api/whiteboard/<id:\d+>'=>'apiwhiteboard/view',
                        'DELETE api/whiteboard/<id:\d+>'=>'apiwhiteboard/delete',
                        'POST api/whiteboard/'=>'apiwhiteboard/create',
                        'PUT api/whiteboard/<id:\d+>'=>'apiwhiteboard/update',
                        
                        ...
                ],
        ],

    ...

Config Routes

config > web.php