Difference between nullable and strict ?

[TheKassaK]

I'm working on a Symfony project in API mode with FosRestBundle and NelmioApiDoc.

So, I have an annotation for a param in my route like :

• @rest\QueryParam(name="code", requirements="[0-9]{4}[A−Za-z]{1}", strict=true, description="Naf Code")
  With this my param code is required both for the FosRest validation and for the Nelmio doc generated.

My question is, if you check the doc : https://symfony.com/doc/master/bundles/FOSRestBundle/annotations-reference.html you can see there is an option nullable but if I replace strict=true by nullable=false my param is not required anymore..

So, what's the strict option exactly ? And what's the nullable option exactly ?

Thanks !