accounts/api/models/ConfirmEmailForm.php

<?php
namespace api\models;

use common\models\Account;
use common\models\EmailActivation;
use Yii;
use yii\base\ErrorException;

class ConfirmEmailForm extends BaseKeyConfirmationForm {

    public function confirm() {
        if (!$this->validate()) {
            return false;
        }

        $confirmModel = $this->getActivationCodeModel();
        if ($confirmModel->type != EmailActivation::TYPE_REGISTRATION_EMAIL_CONFIRMATION) {
            $confirmModel->delete();
            // TODO: вот где-то здесь нужно ещё попутно сгенерировать соответствующую ошибку
            return false;
        }

        $transaction = Yii::$app->db->beginTransaction();
        try {
            $account = $confirmModel->account;
            $account->status = Account::STATUS_ACTIVE;
            if (!$confirmModel->delete()) {
                throw new ErrorException('Unable remove activation key.');
            }

            if (!$account->save()) {
                throw new ErrorException('Unable activate user account.');
            }

            $transaction->commit();
        } catch (ErrorException $e) {
            $transaction->rollBack();
            throw $e;
        }

        return true;
    }

}