GotText is a translation engine for PHP 7 and PHP 5. It can be used instead of gettext, but it's not a drop-in replacement. The main goal of this project is to build a translation engine with gettext features but without any gettext shortcomings. GotText solves most of the fundamental problems of using gettext in PHP and also has an extra functionality on top.
GotText is fully documented and can be built at least on Debian, Ubuntu and CentOS.
The project most likely will remain source-only until someone decides to be the package maintainer.
You can read all the other details at the GotText homepage.