Tila Tequila

Purchasing a spring assist knife, but illegal to carry in PA?

I’m looking into purchasing an SOG Trident folding knife from Dick’s Sporting Goods. This is new to me (I’m not familiar with laws relating o this subject) but from what I hear it is illegal to carry a spring assisted knife in the state of Pennsylvania, regardless of its length. Is this true? If it is, then can I still purchase the knife at the store or is it something I have to purchase off the store’s website? And if that’s the case then is this one of those things where I can own an assisted knife but not be allowed to carry it?