I apologise if this is a stupid question, but I have no clue what to put for these values.
define('SITE_KEY', '**************************');
define('TOKEN', $reportToken);
define('ASSESSMENT_NAME', 'What do I put here?');
define('PROTECTED_ACTION', 'What do I put here?');
define('PARENT_PROJECT', 'projects/project-name');
Based on the information you have provided, it would seem that you are trying to build and create an assessment using reCAPTCHA Enterpise using PHP.
In terms of what is needed in ASSESSMENT_NAME and PROTECTED_ACTION, I would suggest reviewing the following documents to help understand the API and SDK of reCAPTCHA: