Here in NJ, the evidence should have been your hands at the first or second Court appearance, not when you are about to start trial. Talk to your lawyer, ask him what the discovery rules and time frames are in PA. Demand to see all of the evidence the State will use against you. If he does not have it, tell the judge you have asked for the discover and it has not been given to you, so there is no way you can make an intelligent and knowing decision whether to plea or go to trial. If necessary ask for an adjournment to hire another lawyer. Good luck.
This answer does not, nor is it intended to, create an attorney-client relationship; or, constitute either legal advice or attorney advertising. Rather, given the nature of this forum, it is offered solely for information purposes, as a starting point for you to use when speaking directly to a lawyer in your State. Do not assume that the legal conclusions I mention that pertain to NJ are applicable in your State. Since the facts of each case are different, it is critical for you to consult with qualified counsel with whom information can be shared and assessed under an attorney-client privilege, so that competent advice can be obtained on which you can make informed decisions. Contact an experienced criminal defense lawyer admitted to practice in your State before making any decisions about your case.