php 自动提交表单

<form action="http://app.renren.com/pay/web4test/submitOrder" method="post" id="formdata" name="formdata" target="_top"><!--如果正式运行，需要改form的url-->
    <div style="display:none">
        <input type="hidden" name="app_id" value="140996"/>
        <input type="hidden" name="order_number" id="order_number" value="<?php echo $order_id;?>"/>
        <input type="hidden" size="50" name="token" id ="token" value="<?php echo $token;?>"/>
        <input type="hidden" size="50" name="redirect_url" id="redirect_url" value="http://apps.renren.com/mohuanwang"/>     
    
    </div>
</form>

       $url = 'http://localhost/curl/result.php';
       $params = "param=123&param2=333"; //What will be posted
       $user_agent = "Mozilla/5.0 (compatible; MSIE 5.01; Windows NT 5.0)";
       $ch = curl_init();
       curl_setopt($ch, CURLOPT_POST,1);
       curl_setopt($ch, CURLOPT_POSTFIELDS,$params);
       curl_setopt($ch, CURLOPT_URL,$url);
       curl_setopt($ch, CURLOPT_USERAGENT, $user_agent);
       curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);