To answer your question: it depends on the purpose. If you're planning to use the server to advance your skills in languages like PHP or to test your scripts, then yes, you can run a server at home, preferably on your computer now.
However, having servers and all that at home for a hosting company... not worth it. You should look for a datacenter or some dedicated servers, which will make your life a lot easier.
Having servers maintained by datacenters or dedicated servers will not only make your life a lot easier, but without the need to hire more staff to maintain servers, the cooling systems and all that, you also save money.
So, in short: if its for testing your scripts or learning programming languages, then yup, on your PC you could have a server. For a hosting company, no.