A phpinfo.php file is invaluable for confirming that your PHP installation is working, and for viewing its configuration. …
Place the following script, named phpinfo.php, in Apache's document root. On a local installation this might be /var/www/html; on a remote shared hosting account, it might be /usr/www/users/USER.
<?php // Show all information phpinfo(); ?>
In a web browser, view the script. On a local installation, the URL might be http://localhost/phpinfo.php; on a remote host it might be of the form http://example.com/phpinfo.php. If PHP is working you will see a report of its current configuration.
If you wish to confirm that you have successfully changed a configuration variable, simply refresh the browser. Beware, of course, browser caching issues.
When finished, remove phpinfo.php from world accessible servers when you are done with it. Otherwise your setup and potential vulnerabilities will be in the hands of every 14 year old cracker who knows how to Google. On local servers not accessible from the Internet, I usually leave it in place for future use.