Observer Mage::throwException error - status 503 error

Question

I just want to restrict some of the category of products to purchase with other category products,

Workout :

If customer click add to cart using observer compare current add-to-cart product category id & already cart products category id, if the current product category id and cart products category id different trigger observer & display message like, You can not add This special Product, empty cart before add it,

and also vice versa, if cart has other category of products, if customer try to add restricted category products throw exception like If you want Kolu Padi, Purchase alone not mixed with other Products

config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Gta_KolupadiRestrict>
            <version>1.0.0</version>
        </Gta_KolupadiRestrict>
    </modules>
    <global> 
        <models>
            <gta_kolupadirestrict>
                <class>Gta_KolupadiRestrict_Model</class>
            </gta_kolupadirestrict>
        </models>
        <events>
            <checkout_cart_product_add_after>
                <observers>
                    <Gta_KolupadiRestrict_Model_Observer>   
                        <type>singleton</type>
                        <class>Gta_KolupadiRestrict_Model_Observer</class>
                        <method>cartevent</method>
                    </Gta_KolupadiRestrict_Model_Observer>
                </observers>
            </checkout_cart_product_add_after>      
        </events>
    </global>  
</config>

my observer :

    <?php
class Gta_KolupadiRestrict_Model_Observer {

    public function cartevent(Varien_Event_Observer $observer) {

        // Load product
        $product = $observer->getProduct();
        $prodID = $product->getId();
        $_product = Mage::getModel('catalog/product')->load($prodID);

        // get category id
        $categoryIds = $_product->getCategoryIds();

        // check cart
        $cart_qty = (int)Mage::getModel('checkout/cart')->getQuote()->getItemQty();

        // check conditiion cart has other products 
        if(in_array(681, $categoryIds) && $cart_qty > 0) {
            Mage::throwException("You can not add This special Product, empty cart before add it");
        }

        // check if restricted category of products try to  add to cart
        $quote = Mage::getModel('checkout/cart')->getQuote();
        foreach ($quote->getAllItems() as $item) {
            $_product1 = $item->getProduct();

            $categoryIds1 = $_product1->getCategoryIds();
            if(in_array(681, $categoryIds1)) {
                Mage::throwException("If you want Kolu Padi, Purchase alone not mixed with other Products");
                break;
            }
        }
    }   
}
?>

Error :

a:5:{i:0;s:67:"If you want Kolu Padi, Purchase alone not mixed with other Products";i:1;s:1835:"#0 /home/abc/public_html/app/code/local/Gta/KolupadiRestrict/Model/Observer.php(21): Mage::throwException('If you want Kol...')
#1 /home/abc/public_html/app/code/core/Mage/Core/Model/App.php(1358): Gta_KolupadiRestrict_Model_Observer->cartevent(Object(Varien_Event_Observer))
#2 /home/abc/public_html/app/code/core/Mage/Core/Model/App.php(1337): Mage_Core_Model_App->_callObserverMethod(Object(Gta_KolupadiRestrict_Model_Observer), 'cartevent', Object(Varien_Event_Observer))
#3 /home/abc/public_html/app/Mage.php(448): Mage_Core_Model_App->dispatchEvent('checkout_cart_p...', Array)
#4 /home/abc/public_html/app/code/core/Mage/Checkout/Model/Cart.php(290): Mage::dispatchEvent('checkout_cart_p...', Array)
#5 /home/abc/public_html/app/code/local/Cmsmart/AjaxCart/controllers/IndexController.php(315): Mage_Checkout_Model_Cart->addProduct('5071', Array)
#6 /home/abc/public_html/app/code/local/Cmsmart/AjaxCart/controllers/IndexController.php(133): Cmsmart_AjaxCart_IndexController->tryaddAction(Object(Mage_Catalog_Model_Product), Array)
#7 /home/abc/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Cmsmart_AjaxCart_IndexController->indexAction()
#8 /home/abc/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('index')
#9 /home/abc/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#10 /home/abc/public_html/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
#11 /home/abc/public_html/app/Mage.php(683): Mage_Core_Model_App->run(Array)
#12 /home/abc/public_html/australia/index.php(93): Mage::run('australia', 'website')
#13 {main}";s:3:"url";s:100:"/ajaxcart/index/index/?form_key=MtlJbvKkqPQKCLJR&product=5071&related_product=&qty=1&_=1565155804563";s:11:"script_name";s:10:"/index.php";s:4:"skin";s:9:"australia";}

Answer 1

I don't know wether your conditions work, I leave that up to you. The problem with the error comes - I assume - because the addProduct() is not inside a try/catch block.

The default Magento Controller looks like this:

\Mage_Checkout_CartController::addAction
public function addAction()
{
    /* ... */
    try {
        /* ... */
        $cart->addProduct($product, $params);
        /* ... */

    } catch (Mage_Core_Exception $e) {
        /* Handle Magento Exception */
    } catch (Exception $e) {
        /* ... */        
    }
}

So I would check the extension, because it looks horrible and broken: https://github.com/roshu1980/add-computers/blob/446b3bea101c239b8e93a39131cb484221bf5437/app/code/local/Cmsmart/AjaxCart/controllers/IndexController.php#L151-L156

Answer 2

The line $categoryIds = $_product->getCategoryIds(); will give you category IDs in an array format.

So there is no need to use:

if($categoryIds->getCategoryIds()=='681' && $cart_qty > 0  )

instead, use:

if(in_array(681, $categoryIds) && $cart_qty > 0)

Update after checking the observer's code:

Please try this code:

<?php
class Gta_KolupadiRestrict_Model_Observer {

    public function cartevent(Varien_Event_Observer $observer) {
        $product = $observer->getProduct();
        $prodID = $product->getId();
        $_product = Mage::getModel('catalog/product')->load($prodID);
        $categoryIds = $_product->getCategoryIds();
        $cart_qty = (int)Mage::getModel('checkout/cart')->getQuote()->getItemQty();
        // foreach ($categoryIds as $category) {


        if(in_array(681, $categoryIds) && $cart_qty > 0) {
            Mage::throwException("If you want Kolu Padi, Purchase alone not mixed with other Products");
        }


        $quote = Mage::getModel('checkout/cart')->getQuote();
        foreach ($quote->getAllItems() as $item) {
            $_product1 = $item->getProduct();
            // $productCategoryId = $item->getCategoryIds();

                // if ($productCategoryId == '681')  //680 category id
                // {
                //  Mage::throwException("Cart has Special Product you can not add another");
                // }
            $categoryIds1 = $_product1->getCategoryIds();
            if(in_array(681, $categoryIds1)) {
                Mage::throwException("If you want Kolu Padi, Purchase alone not mixed with other Products");
                break;
            }
        }
        // }
    }     
}
?>