freetds is a great, free tool to access your sybase tables with PHP. The setup can be a bit tricky. Use the following to put the environment variables that you need:
<?php
putenv ("SYBASE=/usr/local/freetds");
putenv ("SYBPLATFORM=linux");
putenv ("LD_LIBRARY_PATH=/usr/local/freetds/lib");
putenv ("LC_ALL=default");
putenv ('PATH=\"/usr/local/freetds/bin:$PATH\"');
putenv ("DSQUERY=SYBASE");
?>
Even if not using freetds, you'll need those env vars to make any sybase connection work. Another option is to just load them into your box from the command line.