How can I export fields which are not being displayed in admin grid?

Question

I have a custom admin grid, which shows the feedback given by customers during checkout. I have 19 fields in the custom_table including entity_id, created_at and updated_at.

This is my form view:

This is my grid view:

everything works fine. Now when I export the grid as csv/ xml/ excel, it would only export the fields in the grid, but I want all the data in my database-table to be exported. How can I do that? Also If i apply filter in that grid, only those rows should be exported.

note: customer name and email_id are displayed by joining the sales/order table

This is my _prepareCollection() function in Grid.php

protected function _prepareCollection(){
    $collection = Mage::getModel('feedbacktest/feedback')->getCollection();
    // join the order table to display in the grid.
    $collection->join('sales/order', 'increment_id=order_id', array('orderId'=>'entity_id', 'custName'=>'concat(customer_firstname," ",customer_lastname)', 'custEmail'=>'customer_email'), null,'left');
    $this->setCollection($collection);
    return parent::_prepareCollection();
}

Collection gives me all the data (as I require), but exported data contains only the data in the grid.

Can someone help me on this?

Answer 1

You can add in your grid columns that are visible only on export.
In the _prepareColumns() method add this:

if ($this->_isExport) { 
    $this->addColumn('col_id', array(
        'header' => Mage::helper('helper_alias')->__('Header'),
        'index'  => 'col_id',
    ));
}

Just like any other column, just wrapped in if ($this->_isExport) {.