将自定义字段添加到paypal模块magento 1.9

<?xml version="1.0"?>
<config>
    <modules>
        <Custom_Paypal>
            <version>1.0.0</version>
        </Custom_Paypal>
    </modules>
    <global>
        <helpers>
            <paypal>
                <rewrite>
                    <data>Custom_Paypal_Helper_Data</data>
                </rewrite>
            </paypal>
        </helpers>
    </global>
</config>

<?php
class Custom_Paypal_Helper_Data extends Mage_Paypal_Helper_Data
{
    public function getStandardCheckoutFormFields($quote, $addNewFields = true)
    {
        $paypalFields = parent::getStandardCheckoutFormFields($quote, $addNewFields);
        
        // 添加自定义字段到PayPal请求
        $paypalFields['custom_field'] = $quote->getCustomField();
        
        return $paypalFields;
    }
}

<?php
class Custom_Paypal_Block_Onepage extends Mage_Checkout_Block_Onepage
{
    protected function _construct()
    {
        parent::_construct();
        
        // 添加自定义字段到检出表单
        $this->getCheckout()->setStepData('payment', 'allow', true);
        $this->getCheckout()->setStepData('payment', 'complete', true);
        $this->getCheckout()->setStepData('payment', 'allow_sections', true);
        $this->getCheckout()->setStepData('payment', 'show_sections', true);
        $this->getCheckout()->setStepData('payment', 'code', 'payment');
    }
    
    public function getCustomField()
    {
        // 返回自定义字段的值
        return Mage::getSingleton('checkout/session')->getCustomField();
    }
}

<input type="text" name="custom_field" value="<?php echo $this->getCustomField(); ?>" />