SESSION_SUCCESS_MESSAGE undefined

I upgraded to version 2026, and

$_SESSION[SESSION_SUCCESS_MESSAGE] = $echomessage;`

now returns error SESSION_SUCCESS_MESSAGE undefined from within RouteActionController even though defined namespace and include vendor/autoload:

namespace PHPMaker2026\myNameSpace;

include_once "vendor/autoload.php";

Can you help?

There is no SESSION_SUCCESS_MESSAGE anymore. To set a success message, simply call SetSucessMessage().

Brilliant. Thank you.