I’m a Ruby On Rails Developer and I’m constantly creating some snippets to help my self. But the built-in PHP snippets keeps bugging me.

Does anyone knows how to disable/remove them?

You could remove the snippets and PHP.sublime-completions from your User\PHP folder. Save them in another folder outside of the Packages area in case you need/want to re-instate them. They might also be re-instated on a future ST-Build.