Call to a member function getModelInstance() on null

Question

Getting products from curl request from other store but unable to save data in magento. I'm getting getModelInstance() fatal error. Here is my code

 <?php
 $mageFilename = '../app/Mage.php';
  require_once $mageFilename;

  Mage::setIsDeveloperMode(true);
   ini_set('display_errors', 1);


  umask(0);

    $curl = curl_init();

    $API_ID          = "3";
    $API_URL         = "http://magento.com/component/controller.php";
    $App_key         = "03254254";
    $Functionname    = "get_product_list_by_category_id_and_or_vendor_id";
    $data            = "data";


    $product_id='product_id';
    $name='name';
    $description='description';
    $meta_title='meta_title';
    $meta_description='meta_description';
    $meta_keyword='meta_keyword';
    $tag='tag';
    $model='model';
    $sku='sku';
    $upc='upc';
    $ean='ean';
    $jan='jan';
    $isbn='isbn';
    $mpn='mpn';
    $location='location';
    $quantity='quantity';



    curl_setopt_array($curl, array(
        CURLOPT_URL => $API_URL,
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_ENCODING => "",
        CURLOPT_MAXREDIRS => 10,
        CURLOPT_TIMEOUT => 30,
        CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
        CURLOPT_CUSTOMREQUEST => "GET",
        CURLOPT_HTTPHEADER => array(
            "Appid: 3",
            "Appkey: 03254254",
            "Cache-control: no-cache",
            "Categoryid: 101,102,103,104,105",
            "Functionname: get_product_list_by_category_id_and_or_vendor_id",
            "Limit: 1000",
            "Postman-token: 7e0cbcb4-ad69-7f38-de10-f2387f8477ee",
            "Start: 0",
            "Vendorid: 1474614118"
        ),
    ));

    $response = curl_exec($curl);



    $err = curl_error($curl);

    curl_close($curl);

    if ($err) {
        echo "cURL Error #:" . $err;
    } else {
        $data = json_decode($response);
        $data = $data->data;
       // var_dump($data);
        foreach ($data->get_product_list_by_category_id_and_or_vendor_id as $item) {
            $product = Mage::getModel('catalog/product');

            if ($item->product_id) {
                $product->load($item->product_id);
            }

            $product->setSku($item->sku)
                ->setEan($item->ean)
                ->setProductId($item->product_id)
                ->setName($item->name)
                ->setDescription($item->description)
                ->setKeyword($item->keyword)
                ->setPrice($item->Price)
                ->setQtr($item->Quantity)
                ->setS_descriotion($item->S_description)
                ->setStatus($item->Status)
                ->setVisibility($item->Visibility)
                ->SetWeight($item->Weight)
                // Continue setting all other attribute values
                ->save();


            $stockItem = $product->getStockItem();
            $stockItem->setQty($item->quantity)
                ->setIsInStock($item->quantity > 0)
                ->save();

            /*$result[] =array(
                'id'            => $product->setId()->setData,
                'sku'           => $product->setSku()->setData,
                'name'          => $product->setName()->setData,
                'Status'        => $product->setStatus()->setData,
                'description'   => $product->setDescription()->setData,
                'weight'        => $product->setWeight()->setData,
                'created at'    => $product->setCreatedAt()->setData,
                /*'Price'         => Mage::helper('core')->currency($product->setPrice(), true, false), //." ".$currencyCode,
                'Special_Price' => Mage::helper('core')->currency($product->setSpecialPrice(), true, false), //." ".$currencyCode,
                'Stock'         => $product->setQty()->setData,
                'hasOptions'    => $product->isConfigurable()->setData,
                'image'         => $product->setImageUrl()->setData,
                'category'      => $product->setCategoryIds()->setData,
                'meta_title'    => $product->setMetaTitle()->setData,
                'meta_desc'     => $product->setMetaDescription()->setData,
                'meta_keyword'  => $product->setMetaKeyword()->setData,
                'Reviews'       => $product->setReviewsSummaryHtml()->setData,
                'categories'    => $product->setCategoryNames()->setData,
                'Made-in'       => $product->setCountryOfManufacture()->setData,
                'brand'         => $product->setBrand()->setData,

            );*/



        }

    }

Answer 1

Short answer.
Add after umask(0); (or before it) this Mage::app();

Long answer (may help on future problems)

I've searched for the text getModelInstance in the code and the only occurrence is in the Mage_Core_Model_Config class.
It is used in 3 locations.
2 of them are called from inside the class itself with $this->getModelInstance(). This cannot be the problem because you cannot have $this to be null if you are already inside the class.

The other place is when calling Mage::getModel() and it is called like this self::getConfig()->getModelInstance($modelClass, $arguments);.
This means that Mage::getConfig() returns null for some reason.
The method getConfig only returns self::$_config.

Checking where this config is initialized, you will see that you have to run Mage::app() or Mage::init() or Mage::run() to make it have a value.