Unable to create custom collection of products via Shopify API post
===

I'm trying to create a custom product collection using Sandeep Shetty's shopify.php.
Ive been able to make other functional API calls- displaying products and carts etc. But Im unable to create a custom collection with a 'known-good' list of product ids.
Heres my code:

    $charge = array
        (
            "custom_collection"=>array
            (
                "title"=>"ThisTest",
                "collects"=>array(
                    "product_id"=>96525818,
                    "product_id"=>96393246
                )
            )
        );
        try
        {
            // All requests accept an optional fourth parameter, that is populated with the response headers.
            $my_collect = $shopify('POST', '/admin/custom_collections.json', $charge, $response_headers);

            // API call limit helpers
            echo shopify_calls_made($response_headers); // 2
            echo shopify_calls_left($response_headers); // 298
            echo shopify_call_limit($response_headers); // 300

        }
        catch (ShopifyApiException $e)
        {            
            echo "doh";
            print_r($e);
        }

    }

I'm getting the following error back.


    ShopifyApiException Object
(
    [info:protected] => Array
        (
            [method] => POST
            [path] => /admin/custom_collections.json
            [params] => Array
                (
                    [custom_collection] => Array
                        (
                            [title] => ToddTest
                            [collects] => Array
                                (
                                    [product_id] => 96393246
                                )

                        )

                )

            [response_headers] => Array
                (
                    [http_status_message] => Internal Server Error
                    [http_status_code] => 500
                    [server] => nginx
                    [date] => Mon, 16 Jul 2012 23:23:45 GMT
                    [content-type] => application/json; charset=utf-8
                    [transfer-encoding] => chunked
                    [connection] => keep-alive
                    [status] => 500 Internal Server Error
                    [x-shopify-shop-api-call-limit] => 18/500
                    [http_x_shopify_shop_api_call_limit] => 18/500
                    [cache-control] => no-cache
                    [x-request-id] => f22337df8773ff4fa2f9f384ca21f133
                    [x-ua-compatible] => IE=Edge,chrome=1
                    [set-cookie] => _secure_session_id=50f46da87f21f8a1b458baaf8e97a30a; path=/; secure; HttpOnly
                    [x-runtime] => 0.307888
                )

            [response] => Array
                (
                    [errors] => Error
                )

        )

    [message:protected] => Internal Server Error
    [string:Exception:private] => 
    [code:protected] => 500
    [file:protected] => /home/lolsmg/www/shopify_pinterest/shopify.php
    [line:protected] => 32
    [trace:Exception:private] => Array
        (
            [0] => Array
                (
                    [file] => /home/lolsmg/www/shopify_pinterest/pintrest_ui.php
                    [line] => 65
                    [function] => {closure}
                    [args] => Array
                        (
                            [0] => POST
                            [1] => /admin/custom_collections.json
                            [2] => Array
                                (
                                    [custom_collection] => Array
                                        (
                                            [title] => ToddTest
                                            [collects] => Array
                                                (
                                                    [product_id] => 96393246
                                                )

                                        )

                                )

                            [3] => Array
                                (
                                    [http_status_message] => Internal Server Error
                                    [http_status_code] => 500
                                    [server] => nginx
                                    [date] => Mon, 16 Jul 2012 23:23:45 GMT
                                    [content-type] => application/json; charset=utf-8
                                    [transfer-encoding] => chunked
                                    [connection] => keep-alive
                                    [status] => 500 Internal Server Error
                                    [x-shopify-shop-api-call-limit] => 18/500
                                    [http_x_shopify_shop_api_call_limit] => 18/500
                                    [cache-control] => no-cache
                                    [x-request-id] => f22337df8773ff4fa2f9f384ca21f133
                                    [x-ua-compatible] => IE=Edge,chrome=1
                                    [set-cookie] => _secure_session_id=50f46da87f21f8a1b458baaf8e97a30a; path=/; secure; HttpOnly
                                    [x-runtime] => 0.307888
                                )

                        )

                )

        )

    [previous:Exception:private] => 
)
Im working from example code shopfiy provides but not getting very far. Thank you for any help.