frontend/controllers/ChatController.php

<?php
namespace frontend\controllers;
use common\models\Chat;
use common\models\Message;
use Yii;
use common\models\User;
use yii\data\ActiveDataProvider;
use yii\filters\AccessControl;
use yii\web\Controller;
use yii\web\NotFoundHttpException;
/**
 * Site controller
 */
class ChatController extends Controller
{
    public $defaultAction = 'list';
    public function behaviors()
    {
        return [
            'access' => [
                'class' => AccessControl::className(),
                'rules' => [
                    [
                        'actions' => ['list', 'message', 'message-save'],
                        'allow' => true,
                        'roles' => ['@'],
                    ],
                ],
            ],
        ];
    }
    public function actionList()
    {
        return $this->render('list');
    }
    public function actionMessage($user_id)
    {
        $user = \Yii::$app->user->identity;
        $chat = Chat::find()
            ->where([
            'or',
            ['from_user' => $user_id,],
            ['to_user' => $user_id,],
            ])
            ->andWhere([
                'or',
                ['from_user'=> $user->id,],
                ['to_user'=>  $user->id,],
            ])->one();
        if(!$chat instanceof Chat){
            $chat = new Chat();
            $chat->from_user =  $user->id;
            $chat->to_user =  $user_id;
            $chat->save();
        }
        $post = \Yii::$app->request->post();
        if(isset($post)){
            $message = new Message();
            if($message->load($post, 'Message')){
                $message->chat_id = $chat->chat_id;
                $message->user_id = $user->id;
                $message->save();
                return $this->redirect(['chat/message', 'user_id'=>$user_id]);
            }
        }
        return $this->render('message',[
            'chat' => $chat,
            'user_id' => $user_id
        ]);
    }
}