Virtual Box used in conjunction with Vagrant and a provisioning tool like chef or puppet, are a great set of tools to add to any PHP developers arsenal. These tools can be used so that all developers have the same development environment, and help to maximise dev/prod parity, which makes things like "it works on my machine" a thing of the past.
Vagrant combined with Virtual box and a provisioning tool like chef or puppet fundamentally changes the way developers setup their development environments and develop their web applications. Once configured, vagrant allows developers to spin up a new environment in a couple of commands and allows each developer to have the exact same development environment. As PHP developers, our development environments differ significantly.
Vagrant solves this by allowing developers to create reproducibly development environments on the fly when and where they are needed. Yes, it is true there are now at least half a dozen LAMP installers out there, each one has slight variations on what and how it installs and how it works on different operating systems. Some developers do not use an installer they might decide to compile from source, use what comes with the latest mac osx or develop directly on a server in the cloud. However, the eco-system around PHP is forever changing and setting up reproducible complex development environments in an automated way is extremely useful.
These tools and skills are a great asset for all PHP developers.