I have an instance of SQL Server platform in ArcGIS desktop. I want to connect to the SQLServer database using pdo class and my version of php is 7.0.8. Which ODBC driver will be good to install?
What version of SQL Server are you running? The ODBC Driver 11 for SQL Server provides support for connecting to Microsoft SQL Server 2005, 2008, 2008R2, 2012, and 2014. I suggest that you check that the SQL Server Native Client is installed on the machine running PHP as well. This is a requirement for using the SQLSRV extension in PHP.