A person can use an eBay gift card to pay for items when also paying with their PayPal account. However, you can't just add or transfer the gift card amount to your Pay Pal account to add the money beforehand. When you are on eBay and you go to the checkout page, you will put the redemption code number into the redemption code box on that first page. You will do this before you ever log onto the PayPal site. You can then use the gift card to pay for your purchases. After this is done, any remaining balance on your eBay gift card will then show up in your PayPal wallet.
You have to do work against the strong nuclear force