alipayclient alipayclient = new defaultalipayclient("https://openapi.alipay.com/gateway.do","app_id","your private_key","json","gbk","alipay_public_key","rsa2");
alipayopeninviteordercreaterequest request = new alipayopeninviteordercreaterequest();
request.setbizcontent("{" 
"\"isv_biz_id\":\"2019112510242227500044939\"," 
"\"isv_return_url\":\"https://open.alipay.com/settling/returnbackurl.htm\"" 
"  }");
alipayopeninviteordercreateresponse response = alipayclient.pageexecute(request);
//获取需提交的form表单
string submitformdata = response.getbody();
//客户端拿到submitformdata做表单提交

iaopclient client = new defaultaopclient("https://openapi.alipay.com/gateway.do", "app_id", "merchant_private_key", "json", "1.0", "rsa2", "alipay_public_key", "gbk", false);
alipayopeninviteordercreaterequest  request= new alipayopeninviteordercreaterequest() ;
request.bizcontent="{" 
"\"isv_biz_id\":\"2019112510242227500044939\"," 
"\"isv_return_url\":\"https://open.alipay.com/settling/returnbackurl.htm\"" 
"  }";
alipayopeninviteordercreateresponse response=client.pageexecute(request);
console.writeline(response.body);
string submitformdata = response.body;
//客户端拿到submitformdata做表单提交

$aop = new aopclient ();
$aop->gatewayurl = 'https://openapi.alipay.com/gateway.do';
$aop->appid = 'your app_id';
$aop->rsaprivatekey = '请填写开发者私钥去头去尾去回车，一行字符串';
$aop->alipayrsapublickey='请填写支付宝公钥，一行字符串';
$aop->apiversion = '1.0';
$aop->signtype = 'rsa2';
$aop->postcharset='gbk';
$aop->format='json';
$request = new alipayopeninviteordercreaterequest ();
$request->setbizcontent("{" .
"\"isv_biz_id\":\"2019112510242227500044939\"," .
"\"isv_return_url\":\"https://open.alipay.com/settling/returnbackurl.htm\"" .
"  }");
$result = $aop->pageexecute ( $request); 
//php-sdk执行pageexecute拿到的result即为要提交的form表单数据，客户端拿到result后提交。

https://openapi.alipay.com/gateway.do?timestamp=2013-01-01 08:08:08&method=alipay.open.invite.order.create&app_id=19322&sign_type=rsa2&sign=eritjkeijkjhkkkkkkkhjereeeeeeeeeee&version=1.0&charset=gbk&biz_content=alipayopeninviteordercreatemodel

// 响应为表单格式，可嵌入页面，具体以返回的结果为准
"submit_form" method="post" action="https://openapi.alipay.com/gateway.do?charset=utf-8&method=alipay.open.invite.order.create&sign=k0w1depfqnmqwygbwoaeszejuaiequfjopltwybygix/rskbfy38vuhrnumxpopy9kglktm4nwwz4deqpgxoolaqrzg4ndogoycmwhmvsv5qwkdgwmiw+lc2f9buil+eude8cfnwhm8uwbzlguicraja14htjvt4bieyiprtrmzu0o6/xsbu/i6y4xpr+vj3kwu8gqe82diqbowlyvbuebumc79iavr7xlhqeff/7wqcwgdmo2pnf4tu0cieus7jb0ffcwv/8uyrqfxzmczcdi2p5flmimj4zqp+tbysotvk6tg12stpjqga2u3+zzy1r0knzxcglhl+wwrtx/cu/g==¬ify_url=http://114.55.81.185/opendevtools/notify/do/bf70dcb4-13c9-4458-a547-3a5a1e8ead04&version=1.0&app_id=2014100900013222&sign_type=rsa×tamp=2021-02-02 14:11:40&alipay_sdk=alipay-sdk-java-dynamicversionno&format=json">
"submit" value="提交" style="display:none" >

// 响应为表单格式，可嵌入页面，具体以返回的结果为准
<form name="submit_form" method="post" action="https://openapi.alipay.com/gateway.do?charset=utf-8&method=alipay.open.invite.order.create&sign=k0w1depfqnmqwygbwoaeszejuaiequfjopltwybygix/rskbfy38vuhrnumxpopy9kglktm4nwwz4deqpgxoolaqrzg4ndogoycmwhmvsv5qwkdgwmiw+lc2f9buil+eude8cfnwhm8uwbzlguicraja14htjvt4bieyiprtrmzu0o6/xsbu/i6y4xpr+vj3kwu8gqe82diqbowlyvbuebumc79iavr7xlhqeff/7wqcwgdmo2pnf4tu0cieus7jb0ffcwv/8uyrqfxzmczcdi2p5flmimj4zqp+tbysotvk6tg12stpjqga2u3+zzy1r0knzxcglhl+wwrtx/cu/g==¬ify_url=http://114.55.81.185/opendevtools/notify/do/bf70dcb4-13c9-4458-a547-3a5a1e8ead04&version=1.0&app_id=2014100900013222&sign_type=rsa×tamp=2021-02-02 14:11:40&alipay_sdk=alipay-sdk-java-dynamicversionno&format=json">
<input type="submit" value="提交" style="display:none" >
form>
<script>document.forms[0].submit();script>

{
    "alipay_open_invite_order_create_response": {
        "code": "20000",
        "msg": "service currently unavailable",
        "sub_code": "isp.unknow-error",
        "sub_msg": "系统繁忙"
    },
    "sign": "eritjkeijkjhkkkkkkkhjereeeeeeeeeee"
}