super_globals.php

/**
 * Loads of useful info here: https://www.php.net/reserved.variables.server
 *
 * Double check: always sanitize superglobals before using.
 *
 * ex. $came_from = htmlentitles( $_SERVER[ 'HTTP_REFERER' ] );
 * ex. echo "My username is " . $_ENV[ 'USER' ];
 *
 * lists all server keys and values
 */
foreach ( $_SERVER as $param => $value ) echo "<p>$param = '$value'</p>";