I have custom fields setup for my products post type. In the backend on new product page, I would like to populate a field from the value in a query string in the URL. I am using a custom admin menu with custom links. What is the code thats needed to set a custom field value based on the value of the query string.
I know how $_GET works, I just need to know the custom function to store the value of the query string to the custom field.