Path "/www/wwwroot/yaoitoon.com/resources/cache/manga/Files/ff/91" is not writable, please set a chmod 0777 or any writable permission and make sure to make use of an absolute path !
Additional information provided by error_get_last():
mkdir(): Permission denied in /www/wwwroot/yaoitoon.com/backend/vendor/phpfastcache/phpfastcache/lib/Phpfastcache/Core/Pool/IO/IOHelperTrait.php line 97