A suitable solution for php microservicies

I'm the maintainer of a old php web application birth in 2009 from the scratch (there is no framework, sic.) hosted in a Debian server.

It has been upgraded during the time, extended with new functionalities and now is a huge pile of code. But it works.

There is a plan of restyling the user interface, at least client side. This could be the chance to modularize the application that cover to many areas (relation with clients, contacts with providers, financial account, customer relationship management).

This could be the chance to convert an humongous application in a modular one.

One idea is: use microservicies!

The question is: what is the suitable solution in php?

At the moment I found these solutions:

1) ReactPHP, it is easy to install with Composer but requires a lot of dependencies (e.g. Symfony) to work;

2) Swoole PHP, it's a php module that must be installed with PECL. It's fast but not so easy to install in a Debian production server;

3) Amphp, it is easy to install with composer but has and does not require a lot of dependencies to work;

4) Web server that handles the requests on a different port and also catch PUT,DELETE requests.

Any suggestion that could be applied easily in a Debian machine?