Can a landlord evict a tenant just so they can move back into their own home?

I've been told a landlord can evict a tenant just so the own can move back into their home. Is this true? Property is in Pennsylvania.
Update: Any idea what the law is that supports the landlord??? I can't find the statute online. The tenant is fighting the eviction and I'm unemployed and just want to go home! And yes, I will be moving back in after this is all over. What if there is a valid (legal) lease still in effect?
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