How can PHP developers adjust their code to accommodate the change from register globals to $_GET or $_POST variables?

When transitioning from using register globals to $_GET or $_POST variables in PHP, developers should update their code to explicitly access variables from the superglobals $_GET and $_POST arrays instead of relying on the global scope. This helps improve security and code clarity by clearly indicating the source of the variables being used in the code.

// Before
$username = $_GET['username'];

// After
$username = isset($_GET['username']) ? $_GET['username'] : '';