A $order = Mage::getModel('sales/order')->getCollection() ->addAttributeToFilter('customer_id',$session->getId()) ->getFirstItem(); if ($orders->getSizeValue()) { }
B $orders = Mage::getResourceModel('sales/order_collection') ->addFieldToSelect('*') ->addFieldToFilter('entity_id', $customer->getEntityId()); if ($orders->getSize()) { }
C $orders = Mage::getResourceModel('sales/order_collection') ->addFieldToFilter('customer_id', $customer->getId()); if ($orders->getValue()) { }
D $orders = Mage::getResourceModel('sales/order_collection') ->addFieldToSelect('*') ->addFieldToFilter('customer_id', $customer->getId()); if ($orders->getSize()) { }