OpenCart add to array

This may be very simplistic question but I can't find the answer. I want to add a key/value pair to an array in OpenCart but I can't seem to get it to work. I'm not sure if what I'm adding to is already an array.

In catalog/controller/account/history.php at line 66 there is the definition of an array:-

            $this->data['orders'][] = array(
                'order_id'   => $result['order_id'],
                'name'       => $result['firstname'] . ' ' . $result['lastname'],
                'status'     => $result['status'],
                'date_added' => date($this->language->get('date_format_short'), strtotime($result['date_added'])),
                'products'   => $product_total,
                'total'      => $this->currency->format($result['total'], $result['currency'], $result['value']),
                'href'       => HTTPS_SERVER . 'index.php?route=account/invoice&order_id=' . $result['order_id']
            );

I want to add to this array using VQMod. VQMod won't let me replace a line within the definition. I don't know why, I've tried for a couple of hours, it just won't. So I decided to add a line beneath it like so:-

$this->data['orders']['amountToPay'] = $paymentState['amountToPay'];

This doesn't work. Not even if I type it directly in the page. I reckon I've messed up the syntax but don't see how unless I'm not understanding the array structure.

Any help appreciated.

You can use the following line -

$this->data['orders'][sizeof($this->data['orders'])-1]['amountToPay'] = $paymentState['amountToPay']; 

Because your $this->data['orders'] is also a numeric indexed array which contains collection of associative array.

I think your problem will be solved.

Pretty easy to do this using vQmod. Basically you need to search for

$this->data['orders'][] = array(

and put the line after it. Here's what you need to put in your custom vQmod XML file

<file name="catalog/controller/account/history.php">
    <operation>
        <search position="after"><![CDATA[$this->data['orders'][] = array(]]></search>
        <add><![CDATA['amountToPay' => $paymentState['amountToPay']]]></add>
    </operation>
</file>