Upgrading to PHP 7 on IIS

[srock]

I have a production forum still on vBulletin 4. I have a test forum on vBulletin 5.1. I am trying to upgrade the test forum to the latest 5.2.4 patch level 2 which appears to require a higher version of PHP then I have installed, currently 5.3.8 (x86).

I installed PHP 7.0.9 (x86) and it knocked out my production message board. Rolling back to PHP 5.3.8 and it came right back.

Questions:
1. Is PHP 7.0.9 supported by vBulletin 4? If so, after switching IIS to use PHP 7, is there something I need to do for vBulletin to work properly?

2. I have a 64 bit server. Can I use PHP x64 for vBulletin?

3. Is it possible to have one IIS site use PHP 5.3 (the vBulletin 4 site) but allow another to use PHP 7 (the test forum).

Server info:
Windows Server 2012 x64
IIS 7

How I'm upgrading PHP.

Microsoft Web Platform Installer. Install PHP 7.

IIS Manager
PHP Manager
Change PHP version to 7

[Mark.B]

Out of the vB4 branch, only the 4.2.5 Alpha release is compatible with php 7.
vBulletin 5.2.4 requires a minimum of php 5.5.

You will need to update your vB4 installation to 4.2.3 (which will work with php 5.5), you can then update the 5.1 installation to 5.2.4 (which will also work with php 5.5).

After that you can update php to 7 if you wish.