Hi,
it's a long time ago working with ASA....
There are at least 2 alternatives for binding the php-client to a sybaseclient on your linuxbox.
You have to recompile the PHP-Module.
I don't know about a ready RPM with builtin Sybase Support
1) ODBC is pronounced as a good choice.
Check out for ASA and ODBC for Linux. (iODBC?)
2) ASA can use the Open Client, but it's more tricky.
INstall the "free" Sybase Adaptive Server Enterprise 11.0.3 for Linux. (check out at freshmeat.net) This gives you the possibility to configure PHP --with-sybase=.... Build a listener in the sybase directory to the ASA...
Good luck
Ingo