Are you sure the code you write is the one that gots executed? And are you actually firing that event to start this code?
I'm pretty sure you registered your event properly for (PlayerInteractEvent) and I don't see why it refuses to execute upon click. EDIT: What do you get if you var_dump your $result?
I even tried to put something if $result is null (transfer the player to a server) but nothing happen..idk why
You tried doing var_dump($result); and it didn't throw out any lines in the console? Then, if that's the case your code isn't being executed.
But how ? I mean, I don't see how it's not executed...The form work, I see the buttons but nothing happen, can u make a little example of how it should be and I will test it ?
Update It seemed to be the plugin EssentialsTP and a ShopGUI plugin that was making the forms to not work. Including plugins like BlockSniper. I still have no idea of why these plugins made FormAPI to not work correctly.