How to install memcache on Mavericks? (MAMP)
It seems there are 2 memcache extensions.
There is memcached and memcache the latter one does not seem to be maintained anymore last stable from 2012.

It looks like your code depends on Memcache since you are using brew, you could just do:

brew install php55-memcache


or 

pecl install 


Install brew by issuing:

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"