Hi,
if you create a script like info.php:
<?PHP
phpinfo();
?>
and call it you'll see how php was compiled on top of the info page (the configure options). If there's something like --with-apxs it could work to recompile php. Download the sources from www.php.net and compile it with all the options shown on the info page and additionally with --with-oracle and/or --with-oci8. You must install at least the oracle client on the server and set up the environment variables correctly.
I don't know if this works but it could work. Make a backup of the libphp4.so if php has been compiled as a loadable module.
If the info page shows that php has been compiled with --with-apache you would also have to recompile apache.
In order to successfully compile php you might need to install some gnu tools like make, gcc ....
Regards,
Thomas