PHP DOCUMENT_ROOT Include does not work with CRON

When including libraries or external files in PHP, the variable $_SERVER['DOCUMENT_ROOT'] will not call the external files if the script is run through CRON.

This is because, usually a PHP script would be executed through a /usr/local/bin/php -q directive. Since Apache does not play a role here, the DOCUMENT_ROOT variable will not work.

To ensure that the DOCUMENT_ROOT works, call the script through curl, wget or lynx. As a security measure, apps like wget are disabled on most servers. The alternative option is to get rid of the DOCUMENT_ROOT variable all together.

When including files in PHP scripts, it is best to create an includes.php in the base dir of the application. All scripts in the sub-directories can call the include file through a define path. The includes file can in turn define paths to other dependencies.

Note:

The -q flag suppresses HTTP header output. As long as your script itself does not send anything to stdout, -q will prevent cron from sending you an email every time the script runs. For example, print and echo send to stdout. Avoid using these functions if you want to prevent cron from sending you email.

Note:
The ../dirname directory include path does not work with cron too. The path needs to be included in full

Source:
http://www.modwest.com/help/kb5-125.html

Further Reference:
http://www.us2.php.net/features.commandline