How can I connect to a SQL Server using Windows authentication and the native SQL driver, when the PHP code is executed on a Linux machine under Apache or PHP-FPM ?
The credentials under which the Web server's process (or thread) is running must map to a valid SQL Server login in order to establish a connection.
So basically the question is how to do this with Linux/Apache/PHP-FPM ?
The answer to this question is to use kerberos and a keytab file to store the Windows user credentials and use something like k5start to acquire and renew the kerberos ticket automatically.
This link Connection problem Linux Apache+PHP to MS SQL Server using WindowsAuth / Kerberos ("No Kerberos credentials available") answers the PHP/Apache related part of this question.