You should be able to change the PHP version without downloading an older version of WAMP. I haven't used it in a while (I've been using XAMPP lately) but I think you can right-click the WAMPP icon in the tray and click on the PHP folder. From there I think you can change/check the version.

EDIT: Here's a guide: https://kostasbariotis.com/multiple-...on-wampserver/

I have it set to 'PHP 5.6.31'. That seems to be the default and I get the error with that. What version of PHP should I be running with Mysidia?

You should run PHP 5.4.

Yeah, no. Still not working. I've gone through all the steps of changing the PHP version. It threw up errors so I tried fixing those. NOT WORKING. I give up with this thing. Any news on when Mysidia will be updated? Guess I'm going to try this the old fashioned way. =/

Honestly, I don't think the update's coming since we haven't heard anything about it's progress in years. If v4 is coming though, it probably won't be for another few years.