FreeTDS XAMPP Install - cannot connect via PHP

I can successfully connect to the database using isql command from the shell.  But when I try to connect via php using the odbc_connect method and the same dsn, I get this: Fatal error: Call to undefined function odbc_connect() in /opt/lampp/htdocs/includes/db_login.inc on line 8

I installed PHP ODBC but I do not see any reference to odbc in the php-info() page.  I am wondering if the config files are in the wrong directory to be used by php.  They are in /etc as per the default install and online instructions.  But I also see that in XAMPP, the root directory is /opt/lampp.  So I don't know if I need to build them in the /opt/lampp/etc directory to make them work?

Also, when I put the extension=odbc.so directive in the php.ini in the /opt/lampp/etc directory I get an error starting and stopping XAMPP indicating that it cannot find that file.  But it does not error with that line in the php.ini in the /etc. directory.

Any help would be greatly appreciated!