Magento 1.9 sendTransactional doesn't show value from {{var payment_html}}

Question

I'm using sendTransactional() to send emails programmatically. All working fine beside the variable {{var payment_html}} is empty.

How to pass this value?

below is the code I'm using now.

private function dosend($order, $templateId)
{
    // Set sender information
    $senderName = Mage::getStoreConfig('trans_email/ident_general/name');
    $senderEmail = Mage::getStoreConfig('trans_email/ident_general/email');
    $sender = array(
        'name' => $senderName,
        'email' => $senderEmail
    );

    // Set recepient information
    $recepientEmail = $order->getCustomerEmail();
    $recepientName = $order->getCustomerFirstname();

    // Get Store ID
    $storeId = Mage::app()->getStore()->getId();

    $vars = array(
        'order' => $order,
    );

    $translate  = Mage::getSingleton('core/translate');
    // Send Transactional Email

    Mage::getModel('core/email_template')
        ->setDesignConfig(array('area' => 'frontend', 'store' => $storeId))
        ->sendTransactional($templateId, $sender, $recepientEmail, $recepientName, $vars, $storeId)
    ;

    $translate->setTranslateInline(true);
}

Answer 1

Check out this block of code in /app/code/core/Mage/Sales/Model/Order.php

Generating the payment_html: https://github.com/engineyard/magento-ce-1.9/blob/170c1a51387428fb56f3ada2504d52a2b130360a/app/code/core/Mage/Sales/Model/Order.php#L1282-L1296

Injecting it into the template: https://github.com/engineyard/magento-ce-1.9/blob/170c1a51387428fb56f3ada2504d52a2b130360a/app/code/core/Mage/Sales/Model/Order.php#L1330-L1339

This is not required, but a nice to have: Generating a custom info payment block http://excellencemagentoblog.com/blog/2011/10/28/magento-create-custom-payment-method/