Does the PHP installation work? If so, call phpinfo() in a script..... it will tell you the path to php.ini (or php3.ini if you're running PHP3). It will also tell you the current state of the flag (On or Off).
The ignore_user_abort flag can also be over-riden from it's default value on a script by script or directory wide basis. To over-ride for a single script, place the following code at the top of that script:
ini_set("ignore_user_abort", "Off/On");
On a directory wide basis you can either do it with a .htaccess file or by placing a section for that directory in httpd.conf. The value used, in either case, to over-ride is:
php_value ignore_user_abort Off/On
HTH.
-geoff