integration of paypal on drupal site

hi every on I have created paypal integration while registering i.e. paid registration. my code is following in module

function paidregistration_user($op, &$edit, &$account, $category = NULL){

                switch ($op) {
        case 'validate': {

                                $paypal = array();
                                $paypal['cmd'] = '_xclick';
                                $paypal['business'] = 'sachin.acetechpvtltd@gmail.com';  // doing this here prevents email harvesting
                                $paypal['page_style'] = 'Primary';
                                $paypal['bn'] = 'PP-DonationsBF';
                                $paypal['item_name'] = 'Donation';
                                $paypal['amount'] = '200';
                                $paypal['currency_code'] = 'USD';
                                $paypal['no_shipping'] = '1';
                                $paypal['tax'] = '0';
                                $paypal['lc'] = 'US';
                                $paypal['rm'] = '1';
                                $paypal['return'] = 'http://localhost/drupaldemo/pay';
                                $paypal['cancel_return'] = 'http://localhost/drupaldemo/user/register';

                                // Append the Paypal data to the $form_values['submitted_tree']
                                $data = array_merge($edit, $paypal);

                                // Put the data in a query string
                                $query = http_build_query($data, '', '&');

                                // Set the URL to Paypal's processing site and append the query string
                                $url = 'https://www.sandbox.paypal.com/cgi-bin/webscr?' .$query;
                                drupal_goto($url);
                                print_r($_REQUEST);
                                // Set the webform's confirmation page to Paypal
                                //$node->webform['confirmation'] = $url;

             //drupal_goto();exit;
                             }
            case 'insert' :{
                            print_r($_REQUEST);
                            }
             }
}

and for success return page

function imagemenu_menu()
{
    $items['imagemenu'] = array(
    'title' => 'Ad开发者_StackOverflowd Image',
    'type' => MENU_NORMAL_ITEM,
    );

    $items['pay'] = array(
        'title' => 'Add Image',
        'access arguments' => array('all'),
        'page callback' => 'pay',
        'type' => MENU_NORMAL_ITEM,
    );

return $items;
}





function imagemenu_perm()
{
    return array('all');
}

function pay()
{
    print_r($_REQUEST);
}

here every thing is working fine but does not display data returned from paypal.

any help will be appriciated Thanks

---

Why not just use the existing PayPal module for Drupal? You're re-inventing the wheel here.