PayPal и Php?

У меня есть два способа проверить у пользователя:

1.if user input (Amount field < 5(user credit): do update database the remain amount in my database table. 2.if user input(Amount field) > 5(user credit): Do paypal transaction with the submit form. <form action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post" id="payPalForm"> <input type="hidden" name="item_number" value="01 - General Payment to FreelanceSwitch.com"> <input name="item_name" type="hidden" id="item_name" size="45" value="Posting job"> <input type="hidden" name="cmd" value="_xclick"> <input type="hidden" name="no_note" value="1"> <input type="hidden" name="business" value="seller_1265789181_biz@xxx.xxx.xx"> <input type="hidden" name="currency_code" value="USD"> <input type="hidden" name="return" value="http://freelanceswitch.com/payment-complete/"> Paying Page:<input name="amount" type="text" id="amount" size="5"> <input type="submit" name="Submit" value="Pay"> </form> 

Кто-нибудь может сказать мне, как сделать с формой отправки paypal с условиями.?

Благодарю.

Спасибо @Donny Kurnia, теперь я попробовал:

РЕДАКТИРОВАТЬ::

 function compare_user_credit($paying_price, $user_credit){ $db = &JFactory::getDBO(); $user =& JFactory::getUser(); $user_id = $user->get('id'); if ($paying_price <= $user_credit) { $remain_credit = $user_credit - $paying_price; //DO UPDATE:enough credit update_user_credit_after_paying($remain_credit,$user_id); $action_after_paying = header("Location: index.php?xxxx=5"); } # Case2 direct to paypal with the submit form. else if ($paying_price > $user_credit){ //Need submit form to paypal. $action_after_paying = header("Location: index.php=xxxx&paypal=".$_POST["amount"]); } return $action_after_paying; } $output = '<form method="POST" > '; $output .='<h1>Credit:'.get_credit().'</h1>'; $output .= ' Paying Page <input type="text" name="amount" size=3 max_length=5 />'; $output .='<input type="submit" name="pay" value="pay" />' ; echo $output; if(isset($_POST["pay"])){ compare_user_credit($_POST["amount"], $user_credit); } 

HOw Могу ли я сделать с Paypal в случае 02. (прямо к paypal с формой отправки).