In this recent post to his site Remi Collet shows you how to set up your PHP installation to allow it to work with a Microsoft SQL Server as it's data store.
Here is a small comparison of the various solutions to use a [Microsoft SQL Server](https://en.wikipedia.org/wiki/Microsoft_SQL_Server) database from PHP, on Linux. All the tests have be run on Fedora 23 but should work on RHEL or CentOS version 7.
Several different extensions were tested as a part of making the connection to the SQL server:
- Using PDO, ODBC and FreeTDS
- Using PDO, mssql and FreeTDS
- Using PDO, ODBC and Microsoft® ODBC Driver
- Using the Microsoft® Driver
- Using PDO and the Microsoft® Driver
Each item comes with a list of the requirements involved (other modules/extensions), examples of the configuration changes you'll need to make and some sample code to create the connection.