You will get unmetered(!!) bandwidth with this, however if you burn about 50-100 GB a month they will strongly suggest to hire a dedicated server from them.
Also, no PHP/MySQL is offered, only CGI, and if you ask in their support chat for this some server-owning employee will contact you to host with them. Every RackShack employee has its server and they are all capable of running a webserver, so basically the staff is competing with their boss (nothing wrong with that by the way since it is not RackShack's core business).
RackShack virtual hosting is not worth the effort, you can better ask for a host having his own server since then you can ask for Cpanel (not offered by RackShack).