Predefined Variables are variables in the PHP framework that have existing values assigned, typically associated with the environment a script is being ran in.

For example, this could be information about the script itself, the device running the script, or the server hosting the script.

$_SERVER['SCRIPT_FILENAME'] calls the filename:
/home/eberha54/public_html/infost440/assignment3/predefined.php

$_SERVER['HTTP_USER_AGENT'] calls information about the current user:
Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)