Updated to php 7.3, how to fix errors?

Question

PHP

The guys updated from 7.0 to 7.3 php and of course in the composter uodate project.
I fixed most myself. but some do not understand, here is the error:

Use of undefined constant IdCutomerPackVm - assumed 'IdCutomerPackVm' (this will throw an Error in a future version of PHP)

And here is the code:

if ($project->id == 1) {
                $idProd = IdCutomerPackVm;
            } else if ($project->id == 2) {
                $idProd = IdCutomerPackVd;
            } else {
                $idProd = IdCutomerPackVd;
            }