Webblack card membership only— your guest needs to be 13 or older.
If they are under 16, you have to sign a liability waiver for injury, if they break equipment, etc.
On the app, there is an option to invite a guest.
It sends them a link to fill out with their basic info.
Webthe planet fitness black card is a premium membership that comes with a ton of awesome perks, including access to any planet fitness worldwide, guest.