How to add custom field using displayBeforeCarrier

[Redniks]

Hi, 

I am trying to add a new field in checkout process using a hook "displayBeforeCarrier" and i have a mymodulename.tpl file: 
 

<form class="clearfix" method="post">
    <h6>Proof of purchase:</h6>
    <div>
        <div>
            <span class="custom-radio float-xs-left">
                <input class="ps-shown-by-js" id="invoice_receipt_1" name="invoice_receipt" type="radio" value="1" {if $defaultvalue eq '1'}checked{/if}/>    
                <span></span>
            </span>
            <label for="invoice_receipt_1">
                <span style="padding: 0px 15px;">{l s='Invoice' mod='needinvoicefield'}</span>
            </label>
        </div>
        <div>
            <span class="custom-radio float-xs-left">
                <input class="ps-shown-by-js" id="invoice_receipt_0" name="invoice_receipt" type="radio" value="0" {if empty($defaultvalue) || $defaultvalue eq '0'}checked{/if}/>
                <span></span>
            </span>
            <label for="invoice_receipt_0">
                <span style="padding: 0px 15px;">{l s='Receipt' mod='needinvoicefield'}</span>
            </label>
        </div>
    </div
</form>

 

and I want to retrieve the value of this field at the time of the "actionValidateOrder":

public function hookActionValidateOrder($params)
    {        
        $order = $params['order'];               
        $proof_of_purchase = Tools::getValue('invoice_receipt'); 
        
        $sql = 'UPDATE `'._DB_PREFIX_.'orders` SET `need_invoice` = '.(int)$proof_of_purchase.' WHERE `id_order` = '.(int)$order->id.'';
        Db::getInstance()->execute($sql);
    }

but line:  $proof_of_purchase = Tools::getValue('invoice_receipt');  doesn't work. I think that is because my form was not sent via GET or POST. 

Does anyone know how i can retrieve the "invoice_receipt" value?

Hope someone can help me !

[design4VIP]

bump