Great search product!
I noticed https://forum.xda-developers.com/ is using your product. They are running vBulletin 3.x.
Do you have any details regarding how they integrated Algolia search to their website?
Should I follow the PHP integration guide?
I reached out to them to see if they wanted to share a bit about their implementation.
Otherwise the PHP integration guide can definitely get you started, at least familiar with what the moving parts are.