Magento 1.9 Modifying Admin Customer Grid

Question

I am trying to add a column for "trained_in" on the customer admin page inside my magento site.

I have the following code

    $collection = Mage::getResourceModel('customer/customer_collection')
        ->addNameToSelect()
        ->addAttributeToSelect('trained_in')
        ->addAttributeToSelect('*')
        ->addAttributeToSelect('created_at')
        ->addAttributeToSelect('group_id')
        ->joinAttribute('trained_in','')
        ->joinAttribute('billing_postcode', 'customer_address/postcode', 'default_billing', null, 'left')
        ->joinAttribute('billing_city', 'customer_address/city', 'default_billing', null, 'left')
        ->joinAttribute('billing_telephone', 'customer_address/telephone', 'default_billing', null, 'left')
        ->joinAttribute('billing_region', 'customer_address/region', 'default_billing', null, 'left')
        ->joinAttribute('billing_country_id', 'customer_address/country_id', 'default_billing', null, 'left');

    $this->setCollection($collection);
    //code from Mage_Adminhtml_Block_Widget_Grid::_prepareCollection()
    //since calling parent::_prepareCollection will render the code above useless
    //and you cannot call in php parent::parent::_prepareCollection()
    if ($this->getCollection()) {

        $this->_preparePage();

        $columnId = $this->getParam($this->getVarNameSort(), $this->_defaultSort);
        $dir      = $this->getParam($this->getVarNameDir(), $this->_defaultDir);
        $filter   = $this->getParam($this->getVarNameFilter(), null);

        if (is_null($filter)) {
            $filter = $this->_defaultFilter;
        }

        if (is_string($filter)) {
            $data = $this->helper('adminhtml')->prepareFilterString($filter);
            $this->_setFilterValues($data);
        }
        else if ($filter && is_array($filter)) {
            $this->_setFilterValues($filter);
        }
        else if(0 !== sizeof($this->_defaultFilter)) {
            $this->_setFilterValues($this->_defaultFilter);
        }

        if (isset($this->_columns[$columnId]) && $this->_columns[$columnId]->getIndex()) {
            $dir = (strtolower($dir)=='desc') ? 'desc' : 'asc';
            $this->_columns[$columnId]->setDir($dir);
            $this->_setCollectionOrder($this->_columns[$columnId]);
        }

        if (!$this->_isExport) {
            $this->getCollection()->load();
            $this->_afterLoadCollection();
        }
    }

    return $this;
}

/**
 * override the _prepareColumns method to add a new column after the 'email' column
 * if you want the new column on a different position just change the 3rd parameter
 * of the addColumnAfter method to the id of your desired column
 */
protected function _prepareColumns(){
    $this->addColumnAfter('trained_in', array(
        'header'    => Mage::helper('customer')->__('Trained In'),
        'index'     => 'trained_in'
    ),'name');
    return parent::_prepareColumns();
}

}

However on the front end the column is showing as empty next to each customer but when i dump out the collection it shows ['trained_in'] => 6? A little context :

Trained in was added as a custom attribute inside of magento, and it is also a multiple select field i wish to display.

Answer 1

I already overwrite grid. So my overwrite grid looks like:

app/code/local/SR/MagentoCommunity/Block/Adminhtml/Customer/Grid.php

<?php

class SR_MagentoCommunity_Block_Adminhtml_Customer_Grid extends Mage_Adminhtml_Block_Customer_Grid
{
    /**
     * @param Mage_Customer_Model_Resource_Customer_Collection $collection
     */
    public function setCollection($collection)
    {
        $collection->addAttributeToSelect('trained_in');
        parent::setCollection($collection);
    }

    protected function _prepareColumns()
    {
        parent::_prepareColumns();

        $this->addColumnAfter('trained_in', array(
            'header'    => Mage::helper('customer')->__('Trained In'),
            'index'     => 'trained_in'
        ), 'customer_since');

        $this->sortColumnsByOrder();
        return $this;
    }
}

[Update]

How I created attribute:

app/code/local/SR/MagentoCommunity/sql/sr_magentocommunity_setup/upgrade-0.0.0.1-0.0.0.2.php

<?php
/* @var $installer SR_MagentoCommunity_Model_Resource_Setup */
$installer = $this;

$installer->startSetup();

$installer->addAttribute("customer", "trained_in",  array(
    "type"     => "varchar",
    "backend"  => "",
    "label"    => "Trained In",
    "input"    => "multiselect",
    "source"   => "sr_magentocommunity/customer_attribute_source_trainedin",
    "visible"  => true,
    "required" => false,
    "default" => "",
    "frontend" => "",
    "unique"     => false,
    "note"       => ""
));

$attribute   = Mage::getSingleton("eav/config")->getAttribute("customer", "trained_in");


$used_in_forms=array();

$used_in_forms[]="adminhtml_customer";
$attribute->setData("used_in_forms", $used_in_forms)
    ->setData("is_used_for_customer_segment", true)
    ->setData("is_system", 0)
    ->setData("is_user_defined", 1)
    ->setData("is_visible", 1)
    ->setData("sort_order", 100)
;
$attribute->save();


$installer->endSetup();

app/code/local/SR/MagentoCommunity/Model/Customer/Attribute/Source/Trainedin.php

<?php

class SR_MagentoCommunity_Model_Customer_Attribute_Source_Trainedin extends Mage_Eav_Model_Entity_Attribute_Source_Abstract
{
    /**
     * Retrieve all options array
     *
     * @return array
     */
    public function getAllOptions()
    {
        if (is_null($this->_options)) {
            $this->_options = array(

                array(
                    "label" => Mage::helper("eav")->__("Myoption-1"),
                    "value" =>  1
                ),

                array(
                    "label" => Mage::helper("eav")->__("Myoption-2"),
                    "value" =>  2
                ),

                array(
                    "label" => Mage::helper("eav")->__("Myoption-3"),
                    "value" =>  3
                ),

                array(
                    "label" => Mage::helper("eav")->__("Myoption-4"),
                    "value" =>  4
                ),

            );
        }
        return $this->_options;
    }
}