blueone

If you make a payment to paypal via your CC does the issuer class it as a cash advance or as a purchase when they calculate interest?

Freak

no its treated as a purchase- not as a cash advance (thats presuming you are actually paying someone for something).

Paypal do warn you that if you were to add funds from your c card to your account, and then withdraw them to your bank account you may be charged by your card company for a cash withdrawal, but ts a 'maybe'.
If you want cash, just pay a trusted friend with a paypal account, have them withdraw it to their bank account and then give you the cash. Its a bit long winded, but eliminates the potential for cash % charges.