First check if the web server is working.

Check that PHP is working. Create a foo.php script containing <?php phpinfo(); ?> to debug PHP configuration.

Next make sure you serve the YK-VAL code under the URL you want, and that accesssing the URL reaches the YK-VAL code. PHP error log in the file set by php.ini error_log, by default /var/log/apache2/error.log. Database errors will also be logged into it.

The database needs to be started. Make sure you can access it and the tables.

If ykval-export crashes, you may be running into a compatibility problem between PHP, curl and libpq. See for more information. The workaround is simple:

user@val:~$ sudo mv /etc/php5/conf.d/curl.ini /etc/php5/conf.d/z_curl.ini