Yes, I know that PHP 7.0 removed the extensions needed to connect to MSSQL. FreeTDS was my option prior to PHP 7.0 but now there really is no obvious upgrade path for those
Official MS extension has branch for PHP 7:
There's still lot of things missing, some marked as planned (Linux support is amongst them), nevertheless it could be another solution in the future.
EDIT (09-09-2016): There were already few Linux releases published since March, with CentOS/Ubuntu specific packages and source available. Keep in mind they aren't marked as Production Ready yet.