How to tell Node Reference CCK the Referrer Node using Parameters

I thought I made a note on this, because while my solution could be not elegant, it is a solution that somebody might use, or somebody else might correct in which case it will benefit me. Please let me know if there is a more elegant, effective way of doing this, or if there is a module that does the trick.

The problem:
- How to pass an argument to a CCK input form and tell node reference that this parameter is the node that it wants to pick.

Use:
- My site where I want users to be able to create child nodes of a different content type based on a particular node. For example, passages in a book, and I want users to make interpretations of each passage, several interpretations will have a singular passage as parent.

The information available:
- A lot, including this custom module from open concepts (http://openconcept.ca/blog/ethan/creating_custom_cck_widgets) that does the trick, and which I copied my function from.

The solution:
- I will send the node number by parameter from the referring node, and catch it in the CCK node with the node reference field.
- Take the number from the URL and tell node reference that that number is the referring node.

How:
- Create a CCK nodereference field in the content type which I called interpretation.
- Paste the following code in the "Default value" section "PHP code" field:

$url = request_uri();
$arguments = explode('/', $url);
$nid = array_pop($arguments);

return array(0 => array('nid' => $nid ));

How it works:

When you call the add node function, you add the number of the referring node after the trailing slash "/", the little function breaks it, and selects the node to reference based on that number. Your call URL might look something like:

http://www.example.com/node/add/interpretation/195

Note:
- You will get an error when submitting your field inside the content type... this is because the nodereference module tries to evaluate your PHP expression on the fly. To get over it, take your URL and add "/1" or any number so that when it is tested, it knows it works.