I know that the newer SQLSVR is recommended, but is SQLSVR an absolute 'must' on a server running IIS version 8.5?
The reason for this question is that I have been ask to migrate an existing website from an old server to a new one. I was hoping to avoid or minimize modifying the PHP code and that site has the MSSQL component.
Please excuse if this question seems like a repeat but, I have searched and I just cannot find a clear statement saying that MSSQL is dead.
Thank you for your help and patience is this question is a repeat.
If you use functionality of MSSQL in PHP, then yes, you should use Microsoft Drivers for PHP for SQL Server (SQLSRV).
A quick search on Google like sqlsrv vs mssql leads nice information about comparison and why you should use sqlsrv (at least in my guess).
For IIS version, although I have never been used sqlsrv driver on IIS 8.5, there is no source I found indicates that you cannot use this driver on that version. So, it should be fine with your IIS.