I currently have a server with a VB 3 X on it, running php 5.3.26 - I am installing a new xenforo instead of updating, and plan to eventually turn the old vb into a read only archive, and transition users slowly to the new xenforo board. (This is because I have so many customizations and mods installed on my old vb board I don't think I can transfer everything easily to the new board. Would rather leave the old one as is for now, and slowly transition ppl to a clean install of xenforo)
if I install xenforo now, and then upgrade to php 4 later, will it cause problems? At the moment, I don't want to mess with my existing board -
@jilly, we were in very similar situation with one of our recent project and we ended up running 2 php versions for supporting old vBulletin forum. As Brogan already suggested XF not got any issue with both php versions.
If your board is active, its highly recommended to test everything on staging environment to check the compatibility - as its not always the core vB which creates trouble but sometimes customization/plugins can really put you in bad position.