There is a link to PA laws in the sticky on the top of this forum. But I doubt VERY much if such a law exists. It definitely would NOT be illegal to require a tenant to sign a new lease. Since a month to month lease can be terminated with one month's notice from either party it makes no sense to require such.
When a lease expires, both the tenenat and landlord have options to continue it. If the tenant does not want to renew the lease, then they have to vacate unless the landlord agrees to a periodic (month to month) occupancy.