Why is productCategory returning NULL in my GraphQL code?

[chen4eto]

Hello, I am trying to create a product with GraphQL and my code for productCategory is that:  

$variables['productCategory'] =  array([

                "productTaxonomyNodeId" =>"2879"

            ]);

I give the TaxionmyId but when the product is created and I get the product data,  productCategory returns NULL.
I can't find where is the problem with my code. I get the id from https://help.shopify.com/txt/product_taxonomy/en.txt?shpxid=2761127d-AEE3-4A5E-478F-4B6E19271E85. Is it possible that I have to submit some other id?

[chen4eto · Accepted solution]

I find what is the problem:

First, I don't provide productCategory in the input array, and secondly, I need to add the 'productTaxonomyNodeId' global id, which looks like this gid://shopify/ProductTaxonomyNode/ 2879