What is better Null or empty string in ValueObject?

Question

PHP

Which is better to use string which will be in ValueObject or null?

public function __construct(Request $request)
    {
        $this->fullname = $request->request->get('fullname', null);

Whole constructor:

public function __construct(Request $request)
    {
        $contactInfo = $request->request->get('contactInfo');

        $this->fullname = $request->request->get('fullname', null);
        $this->email = $contactInfo['email'] ?? null;
        $this->phone = $contactInfo['phone'] ?? null;
        $this->linkedInUrl = $contactInfo['linkedInUrl'] ?? null;
        $this->currentCompany = $request->request->get('current_company', null);
        $this->jobId = $request->request->get('job_id', null);
    }

Answer 1

You receive and process GET parameters, a normal GET parameter is a string.
"In the right way" -

$this->fullname = $request->request->get('fullname', '');

Creating a NullObject in this case is overkill, PHP is one of the few PLs where a string is not an object. Null would also fit, but it's "not Orthodox".