We found that using the Sybase Libs for MS-SQL server 6.5 and below works really well.
1. Download the Sybase database version that is free for development and deployment (11.0.3 I believe). Install it. You dont need to configure the database though.
2. Setup the interfaces file to point to your SQL Server. Look at the examples that might be in there.
3. Login into your Linux box as the sybase user, and test the connection by using isql:
isql -U<sql-server username> -P<password> -S<interfaces file server name>
run a query and this should be done in 10 minutes or less (not counting the download).
4. Compile apache/php as instructed, adding the -with-sybase=/path/to/sybase
This should pretty much do it. I can e-mail you interface files examples if necessary.
PHP, Perl, SQL Programming at http://www.mentalobjects.com