Magento: Load products from selected categories in magento

list.phtml

<?php
$categories = array(8,22);
$collection = mage::getModel('catalog/product')->getCollection()
                        ->addAttributeToSelect('*')
                        ->addAttributeToFilter('status',1)
                        ->joinField('category_id',
                                    'catalog/category_product',
                                    'category_id',
                                    'product_id=entity_id',
                                    null,
                                    'left')
                        ->addAttributeToFilter('category_id', array('in' => $categories));

$collection->getSelect()->group('e.entity_id');
?>