Warning: substr() expects parameter 1 to be string, object given in Cache/Backend/Redis.php on line 1218

[ilnytskyi]

Sometimes we randomly get errors like this

Warning: substr() expects parameter 1 to be string, object given in /var/www/html/vendor/colinmollenhour/cache-backend-redis/Cm/Cache/Backend/Redis.php on line 1218

the part of call stack:

Exception: Warning: substr() expects parameter 1 to be string, object given in /var/www/html/vendor/colinmollenhour/cache-backend-redis/Cm/Cache/Backend/Redis.php on line 1218 in /var/www/html/vendor/magento/framework/App/ErrorHandler.php:61
Stack trace:
#0 [internal function]: Magento\Framework\App\ErrorHandler->handler(2, 'substr() expect...', '/var/www/prod.s...', 1218, Array)
#1 /var/www/html/vendor/colinmollenhour/cache-backend-redis/Cm/Cache/Backend/Redis.php(1218): substr(Object(Credis_Client), 2, 3)
#2 /var/www/html/vendor/colinmollenhour/cache-backend-redis/Cm/Cache/Backend/Redis.php(467): Cm_Cache_Backend_Redis->_decodeData(Object(Credis_Client))
#3 /var/www/html/vendor/magento/zendframework1/library/Zend/Cache/Core.php(306): Cm_Cache_Backend_Redis->load('b59_TRANSLATE_P...', false)
#4 /var/www/html/vendor/magento/framework/Cache/Frontend/Adapter/Zend.php(55): Zend_Cache_Core->load('b59_TRANSLATE_P...')

We noticed this line Cm_Cache_Backend_Redis->_decodeData(Object(Credis_Client))

The question: In this method \Cm_Cache_Backend_Redis::load The construction $this->_redis->hGet(self::PREFIX_KEY.$id, self::FIELD_DATA); can return something else than bool|string ?

In signature we see this

maybe it's better to change if expression like this?

        if ($data === NULL || is_object($data)) {
            return FALSE;
        }

the app may not expect to get an object