Magento direct sql query not working in my dynamic adminhtml module config

Question

Following this tutorial I've implemented a dynamic key => value pair setting in my magento adminhtml backend module config.

So, this is my system.xml

<shipping_method_mapping translate="label">
    <label>Shipping Method Mapping</label>
    <comment><![CDATA[Select an active shipping method in magento and map it to the code used by Asendia.]]></comment>
    <frontend_model>infiniteconnect/fieldasendia</frontend_model>
    <backend_model>adminhtml/system_config_backend_serialized_array</backend_model>
    <source_model>infiniteconnect_adminhtml/system_config_source_dropdown_activeshippingmethods</source_model>
    <sort_order>4</sort_order>
    <show_in_default>1</show_in_default>
    <show_in_website>0</show_in_website>
    <show_in_store>0</show_in_store>
</shipping_method_mapping>

and this is my Activeshippingmethods.php (dropdown source model):

class Intellibi_InfiniteConnect_Adminhtml_Model_System_Config_Source_Dropdown_Activeshippingmethods
{
    public function toOptionArray()
    {
        // Init Option Array
        $optionArray = array();

        // Load Magento DB Connection
        $resource = Mage::getSingleton('core/resource');
        $readConnection = $resource->getConnection('core_read');

        // Query Magento DB
        $active_shipping_methods = $readConnection->fetchAll(
            "SELECT DISTINCT `shipping_description` AS `name` FROM ". $resource->getTableName('sales_flat_order'));

        // Build Option Array
        foreach ($active_shipping_methods as $active_shipping_method) {
            $optionArray[] = array(
                'value' => md5($active_shipping_method['name']),
                'label' => Mage::helper('infiniteconnect')->__($active_shipping_method['name'])
            );
        }

        // Finished
        return $optionArray;
    }
}

When I test this locally on my wamp installation; it works great:

However, when I upload this to my remote DEV server running LEMP stack, the behaviour changes and the config screen breaks/does not render correctly like this:

If I modify my Activeshippingmethods.php dropdown source model and comment out all the direct query stuff and return an empty array, then the config screen doesn't break and renders correctly - so this is why I thought there's a problem with the direct query...

I've already checked if my remote linux server has entries in sales_flat_order table and it does (58 distinct shipping_description).

Any idea why this isn't working correctly on a linux server, but it's fine on the WAMP server for some reason? Is this some sort of issue with my module not having the correct ACL to use core_read connection?

Answer 1

I've solved the problem by updating my drop down source model like this:

public function toOptionArray()
{
    // Init Option Array
    $optionArray = array();

    // Query Magento & Build Option Array
    $collection = Mage::getModel('sales/order')->getCollection();
    $collection->addAttributeToSelect('shipping_description');
    $collection->getSelect()->distinct(true);
    foreach ($collection as $order) {
        $optionArray[] = array(
            'value' => md5($order->getShippingDescription()),
            'label' => str_replace("'", "\'", $order->getShippingDescription())
        );
    }

    // Finished
    return $optionArray;
}

The selection options were used inside javascript, which broke when any "labels" have a single quote in them. So I had to explicitly escape it...