What changes were made in PHP 4 regarding passing variables via URL?

In PHP 4, the default behavior for passing variables via URL was changed to disable the register_globals directive for security reasons. This means that variables cannot be directly accessed via the URL without explicitly using the $_GET or $_REQUEST superglobals. To fix this issue, you should update your code to use $_GET or $_REQUEST to access variables passed via the URL.

$variable = $_GET['variable_name'];
echo $variable;