Automated deployment PHP in CI environment (Jenkins)
Looks good overall. I haven't personally used Sonar (but aware of it) or Capistrano (never even heard of this one), so can't comment on those.
Maven is a dependency, build and deployment tool, mainly for Java projects. You are already taking care of the "build" with Jenkins, so don't worry about Maven.
As for deployment, I wrote a very detailed explanation here how to deploy Jenkins builds. Jenkins is fully capable of doing your deployment, so why bother looking to add another tool into the mix? The only thing you need is a bash (or batch, depending on your environment) script to take your PHP files (I advise to zip them up as part of the build job) and copy/deploy them on the remote server.
If you have more specific question, ask away.
There are a few services for automated deployments as far as I know and they are much easier to configure. So for example it can be integrated to Dropbox and automatically deploy code to repos/live even if there is a few developers are working on it. Example: http://unbouncepages.com/the-magicbox/