I ended up tangled in knots with this at the start of the year before Phabricator started supporting PHP 7(.1) … I used Remi’s PHP7 repo to achieve this.
The issue I had was that there was a chain of dependencies based around the default 5.4 CentOS install that work something like this …
OpCache requires PHP 5.5 minimum to run, so you need to get a 5.6 to run that.
Once you have 5.6 installed you then need APCu 5.1.4 (maximum) in order to be able to run it, because after that 5.6 is deprecated as its out of support (except security patches) and current versions only support PHP 7.
I ended up in a “sweet” spot of
Zend OpCahce 7.0.5
and that worked okish for a couple of months, primarily because APCu kept causing Apache errors and it would survive 5-7 days before flat out bombing the server. As soon as Phabricator moved to PHP 7.1 I ditched all those legacy versions and moved straight up.
I would really recommend doing the same to save you from pain later on.