src/paySystems/YandexKassaPaySystem.php
public function checkRequestMD5($request)
    {

        //return true;

        $str = $request['action'].";".
            $request['orderSumAmount'].";".$request['orderSumCurrencyPaycash'].";".
            $request['orderSumBankPaycash'].";".$request['shopId'].";".
            $request['invoiceId'].";".$request['customerNumber'].";".$this->shop_password;

        \Yii::info("String to md5: ".$str, static::class);

        $md5 = strtoupper(md5($str));
        if ($md5 != strtoupper($request['md5'])) {
            \Yii::error("Wait for md5:".$md5.", recieved md5: ".$request['md5'], self::class);
            return false;
        }
        return true;
    }
public function checkRequestMD5($request)
    {

        //return true;

        $str = $request['action'].";".
            $request['orderSumAmount'].";".$request['orderSumCurrencyPaycash'].";".
            $request['orderSumBankPaycash'].";".$request['shopId'].";".
            $request['invoiceId'].";".$request['customerNumber'].";".$this->shop_password;

        \Yii::info("String to md5: ".$str, static::class);

        $md5 = strtoupper(md5($str));
        if ($md5 != strtoupper($request['md5'])) {
            \Yii::error("Wait for md5:".$md5.", recieved md5: ".$request['md5'], self::class);
            return false;
        }
        return true;
    }
Checking the MD5 sign.
@param  array $request payment parameters
@return bool true if MD5 hash is correct