I have struggled a lot to make PHP connect to a MS SQL server from under a Linux (using FreeTDS).
I installed the latest FreeTDS and tried to use usual host:port to connect to a server.
Finally when I configured freetds.conf like that:
host = 192.168.17.17
port = 1433
tds version = 7.0
and used mysrvalias instead of the 192.168.17.17:1433, it worked!