I’m using 3.1.6, the last version before v4 until someone confirms emoncms is ok with v4>. So the command to use would be
sudo pecl install redis-3.1.6
(for the benefit of other readers, I note you are actually running as root so don’t need sudo)
I have not recommended changing the guide(s) as it would require explanation and possibly cause further confusion down the line and we have not long cleared up the confusion brought about by the 1st emonpi image, IMO it would be better to confirm the position with emoncms and fix if needed. I had no idea such a core question would go unresolved for so long.
 just hit enter to answer the question, it will use the default answer offered “no”
I’m not disagreeing with you, but I have raised an issue to discuss the matter (over 5mths ago) and it has fallen on deaf ears, I’ve pointed out it might break so a decision should indeed be made to test/fix emoncms or plug the hole with a edit to the guides, but it’s not my decision to make, if it was, it would be tested and fixed already.
I’m not able to confirm if the emoncms code is safe or not, v4+ might be perfectly ok to use, I have no idea. I only reported the “possible breaking changes” for someone that knows to confirm and I choose to use 3.1.6 in the interim rather than using my live server as a guinea pig.
 Also for the benefit of other readers, what we’re discussing here is not “Redis” the in memory database, but the “phpredis” PHP extension that is referred to as just “Redis” in the PHP modules listings.