Predefined Variables (Superglobals) in PHP

Examples

$_SERVER['SERVER_NAME'] (server host name): ssaparov.soisweb.uwm.edu

$_SERVER['SCRIPT_NAME'] (current script path): /infost440/a3/predefined.php

$_SERVER['HTTP_USER_AGENT'] (browser info): Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)

Explanation (30+ words)

Predefined variables in PHP are built-in variables that already exist and provide information about the request, server, and user environment. Many of them are superglobals like $_SERVER, $_GET, and $_POST, which are available inside any script without needing to be declared first.