Sorry for not responding for some time, i figured it out just a few minutes ago. On the commandline, php -i says that sqlsrv is enabled, but not with <?php echo phpinfo(); ?> this doedn't says anything about sqlsrv. In php_error_log it prints "Unable to load dynamic library D:\xampp\php\ext\php_pdo_sqlsrv.dll", but the file exists with the same permissions as the other extensions.

Really strange, so i checked the dependencies of the dll file, and i found that there is a missing dll called "msvcp110.dll" ... long story short, i installed "Visual C++ Redistributable for Visual Studio 2012" and it worked!

I really hate windows for not managing dependencies like every linux system does. (Edit: "Visual C++ Redistributable" wasn't on the requirements list of sqlsrv)

Thanks you very much for your goodwill to help me^^