Convert PHP DB Code from MSSQL to SQLSRV libraries

I have a client with a website custom written for them. They have a new SQL 2016 server so the old PHP 5.2 MSSQL Libraries won't connect. All the code appears to be in one [login to view URL] in the Lib folder and its not a great deal of code - The rest of the side used the Functions declared there to access data. I've had a crack at getting my head round it with limited PHP experience and very rare dips into coding and its doing my head in as I would need to spend hours on it.