Php PayPal IPN模拟器自定义文本字段

我设置了以下PayPal按钮：

   <form action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_top">
       <input type="hidden" name="cmd" value="_s-xclick">
       <input type="hidden" name="hosted_button_id" value="SN3834XQZMRCW">
       <table>
           <tr><td><input type="hidden" name="on0" value="Minecraft Username:">Minecraft Username:</td></tr>
           <tr><td><input type="text" name="os0" maxlength="200"></td></tr>
           <tr><td><input type="hidden" name="on1" value="TeamSpeak UID:">TeamSpeak UID:</td></tr>
           <tr><td><input type="text" name="os1" maxlength="200"></td></tr>
       </table>
       <input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_subscribeCC_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
       <img alt="" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
   </form>

在您询问之前，我似乎无法使用模拟器发送这些自定义字段，除非这些字段封装在自定义字段中？这里似乎缺少文档和帮助。谢谢你的帮助

$_POST['TeamSpeak UID:'];