Is it possible to integrate amember into tiki wiki, because that script does not have any possibility to have a payment system in it.
You can protect the tiki wiki folder as a whole with Amember today. This "walled garden" approach, however, means that only members would be able to see the content and it would not be a single sign. One thing I have done in the past, however, is a single sign on to VBulletin (via Amember) and then a Mod to VBulletin for Single Sign On to Tiki Wiki.. sort of a roundabout way of getting there, but it worked.
How come I never found that Vbulletin mod? Anyway, doesn't matter. I've found a fully integrated Vbulletin wiki for $40. Here it is: http://www.crackedeggstudios.com/vault.php?egg=The Arsenal:CES VaultWiki I'm very pleased with it. Another option I tried: Amember + Moodle, as Moodle has its own wiki. Moodle is free and so is the plugin for it, here http://www.amember.com/p/Integration/Moodle/ I couldn't get that to work, even after Amember support had fixed the various login problems it caused. But lots of people do use this combination, starting with the big successful teachingsells.com site.