There have been a couple attempts at passing a knife rights bill in PA in recent years, but nothing had come of it. The only universal law in PA that matters is that you can't carry switchblades or gravity knives in public.
Local ordinances can be, and sometimes are, more restrictive. Philadelphia still has the most restrictive knife ban in the country. No one in Philadelphia may carry any bladed tool in public unless it is required for their job and they are on the job.
Technically, even an off duty police officer, FBI agent, etc cannot possess a knife in public in Philadelphia.