基于AuthClient的微信OAuth2认证写下，网上资料少，有也是比较老的,帮助下新手吧。 [ 2.0 版本 ]

https://github.com/yiisoft/yii2-authclient/blob/master/docs/guide/installation.md
这里要先配置组件。大概看官方文档，我下面写一些核心的东西

namespace frontend\components;

use Yii;
use yii\authclient\OAuth2;
use yii\web\HttpException;
use yii\authclient\OAuthToken;

class WeixinAuth extends OAuth2
{

    public $authUrl = 'https://open.weixin.qq.com/connect/oauth2/authorize';
    public $tokenUrl = 'https://api.weixin.qq.com/sns/oauth2/access_token';
    public $refreshUrl = 'https://api.weixin.qq.com/sns/oauth2/refresh_token';
    public $apiBaseUrl = 'https://api.weixin.qq.com';
    
    //构建初始访问威信URL准备去拿code
    public function buildAuthUrl(array $params = [])
    {
        $defaultParams = [
            'appid' => $this->clientId,
            'redirect_uri' => $this->getReturnUrl(),
            'response_type' => 'code',
            'scope' => 'snsapi_userinfo',
        ];

        if ($this->validateAuthState) {
            $authState = $this->generateAuthState();
            $this->setState('authState', $authState);
            $defaultParams['state'] = $authState;
        }
        $url = $this->composeUrl($this->authUrl, array_merge($defaultParams, $params));
        return $url . '#wechat_redirect';
    }

    //拿到code后也就是$authCode去拿accessToken;拿到后传给AuthHandler，并再拿到一个authclient对象。
    public function fetchAccessToken($authCode, array $params = [])
    {
        if ($this->validateAuthState) {
            $authState = $this->getState('authState');
            if (!isset($_REQUEST['state']) || empty($authState) || strcmp($_REQUEST['state'], $authState) !== 0) {
                throw new HttpException(400, 'Invalid auth state parameter.');
            } else {
                $this->removeState('authState');
            }
        }
        $defaultParams = [
            'appid' => $this->clientId,
            'secret' => $this->clientSecret,
            'code' => $authCode,
            'grant_type' => 'authorization_code',
            'redirect_uri' => $this->getReturnUrl(),
        ];
        $request = $this->createRequest()
            ->setMethod('GET')
            ->setUrl($this->tokenUrl)
            ->setData(array_merge($defaultParams, $params));
        $response = $this->sendRequest($request);
        $token = $this->createToken(['params' => $response]);
        $this->setAccessToken($token);
        return $token;
    }


    public function refreshAccessToken(OAuthToken $token)
    {//刷新accesstoken这一步我还没有测试。
        $params = [
            'appid' => $this->clientId,
            'grant_type' => 'refresh_token',
            'refresh_token' => $this->clientSecret,
        ];
        $params = array_merge($token->getParams(), $params);
        $request = $this->createRequest()
            ->setMethod('POST')
            ->setUrl($this->refreshUrl)
            ->setData($params);
        $response = $this->sendRequest($request);
        $token = $this->createToken(['params' => $response]);
        $this->setAccessToken($token);
        return $token;
    }




    protected function initUserAttributes()
    { //这一步是拿认证后的用户 详细信息，供AuthHandler处理，比如绑定会员、添加新会员等。逻辑自行处理
        $oauthToken = $this->getAccessToken();
        $defaultParams = [
            'access_token' => $oauthToken->params['access_token'],
            'openid' => $oauthToken->params['openid'],
            'lang' => 'zh-CN'
        ];
        $request = $this->createRequest()
            ->setMethod('GET')
            ->setUrl('sns/userinfo')
            ->setData($defaultParams);
        return $this->sendRequest($request);
    }

    protected function defaultName()
    {
        return 'weixin';
    }

    protected function defaultTitle()
    {
        return 'weixin';
    }


}


<?php
namespace frontend\components;

use app\models\Auth;
use app\models\User;
use Yii;
use yii\authclient\ClientInterface;
use yii\helpers\ArrayHelper;

/**
 * AuthHandler handles successful authentication via Yii auth component
 */
class AuthHandler
{
    /**
     * @var ClientInterface
     */
    private $client;

    public function __construct(ClientInterface $client)
    {
        $this->client = $client;
    }

    public function handle()
    {
        $attributes = $this->client->getUserAttributes();
        $email = ArrayHelper::getValue($attributes, 'email');
        $openid = ArrayHelper::getValue($attributes, 'openid');
        $nickname = ArrayHelper::getValue($attributes, 'login');


        /* @var Auth $auth */
        $auth = Auth::find()->where([
            'source' => $this->client->getId(),
            'source_id' => $id,
        ])->one();

        if (Yii::$app->user->isGuest) {//如果是未登录账号就处理添加账号
           
        } else { // 已登录用户就与威信号绑定

        }
    }

    /**
     * @param User $user
     */
    private function updateUserInfo(User $user)
    {
        $attributes = $this->client->getUserAttributes();
        $github = ArrayHelper::getValue($attributes, 'login');
        if ($user->github === null && $github) {
            $user->github = $github;
            $user->save();
        }
    }
}


//这里主要是拿到authtoken给authhandler后反回一个authclient的对象
use app\components\AuthHandler;

class SiteController extends Controller
{
    public function actions()
    {
        return [
            'auth' => [
                'class' => 'yii\authclient\AuthAction',
                'successCallback' => [$this, 'onAuthSuccess'],
            ],
        ];
    }

    public function onAuthSuccess($client)
    {
        (new AuthHandler($client))->handle();
    }
}