Sure, by CI I mean continuous integration, which is a huge topic but with a simple goal, which is to be able to safety introduce changes to a project by one or more developers.
It's usually related with solid testing strategies, static code analysis and the software that puts both things together.
- follow clean code as much as you can, as you would with any other language
- do not rely blindly in the abstractions/magic many frameworks provide: try to understand what's under the hood
- avoid software that rely on annotations
- don't miss the chance to apply domain driven design in PHP. It's a language that allows you to beautifully model domains so don't miss the chance
- have fun, it's a great language to bring value quickly
- spend time setting up your CI policies