What is the significance of using $_GET['id'] or $_POST['id'] instead of $id in the code snippet?

Using $_GET['id'] or $_POST['id'] instead of $id in the code snippet is significant because it helps prevent security vulnerabilities such as SQL injection attacks. By accessing the id parameter directly from the superglobal arrays $_GET or $_POST, the input is sanitized and validated automatically. This ensures that the data received is safe to use in database queries or other operations.

$id = isset($_GET['id']) ? $_GET['id'] : null;

// Now $id contains the sanitized and validated value of the 'id' parameter