Pretty sure there is something weird about that. I think @pb66 is the expert on this.
Look at Updating system libraries used by emoncms as well. It starts off talking about Mosquitto, but then talks about redis. Also search on pecl in the community.
Best way is to follow the self install instructions. they are there for a reason.
[edit] this post probably most relevant Updating system libraries used by emoncms - #20 by pb66