[Partially from the PHP website, under Sybase-CT]
First get the linux ASE from sybase (maybe the ctlibs provided at php.net will do fine, too) Install the ASE rpm. (some distributions don't have system libs etc in the rpm database so you might get some dependency errors. If your systems fits the requirements install with "ignore dependencies") Recompile php with option
--with-sybase-ct=/dirtoyoursybasehome
Then you need to set the env variable for (at least)your apache user by export SYBASE=/dirtoyoursybasehome. Now you need to set up your servers (like DSNs for ODBC). Edit the file $SYBASE/interfaces and add your server entries (look for the example interfaces file in the sybase-ct driver that you can download from the PHP website. It doesn't work but it has an example "interfaces" file in it, the Sybase ASE is picky 😉:
Now you can check your config by using
$SYBASE/bin/isql -S SERVERNAME -U DBUSER -P PASSWD
Try this! If this works, you are sure that you have the Sybase CT drivers work. So if you get a prompt you have connected to your sybase! Hurray! Now you can try with php
$db=sybase_connect(server, user,pwd), and that's all!