php - 支付宝移动支付，服务端对异步通知信息验签的时候验签失败

支付宝异步通知数据形式如下，

$arr=array (
  'discount' => '0.00',
  'payment_type' => '1',
  'subject' => '测试02',
  'trade_no' => '2016031.............2958619',
  'buyer_email' => '18776152065',
  'gmt_create' => '2016-03-14 17:04:52',
  'notify_type' => 'trade_status_sync',
  'quantity' => '1',
  'out_trade_no' => '16031238100064254059',
  'seller_id' => '2099122451677261',
  'notify_time' => '2016-03-14 17:04:53',
  'body' => '测试02',
  'trade_status' => 'TRADE_SUCCESS',
  'is_total_fee_adjust' => 'N',
  'total_fee' => '0.01',
  'gmt_payment' => '2016-03-14 17:04:52',
  'seller_email' => 'xxx@126.com',
  'price' => '0.01',
  'buyer_id' => '2065912804441725',
  'notify_id' => '2cf4b6638.............c176e3f3lk2',
  'use_coupon' => 'N',
  'sign_type' => 'RSA',
  'sign' => 'Q3uCDyyCs/nODpHaUeCb1HqGINlQ3AxOr40MUN.............Br40MU=',
)

对数组按KEY首字母排序

ksort($arr);

按官方文档做法，排除掉sign_type,sign然后拼成下面形式的待签名支付串 $SemiFinishedSign

body=Hello&buyer_email=13788888888&buyer_id=2088002007013600
.................................................................................
trade_no=2014040311001004361525&trade_status=TRADE_FINISHED&use_coupon=N

执行下面代码验签！

$pukey=file_get_contents('alipay_public_key.pem');
$publickey=openssl_pkey_get_public($pukey);
$verify=(bool)openssl_verify($SemiFinishedSign, base64_decode($arr['sign']), $publickey);
echo $verify?'验签成功':'验签失败';

用于支付的公私钥都没有问题，对任意字符，openssl_sign();openssl_verify();都能通过

但是验签总是失败，求指导！！

--------------------------更新 2016-03-15-----------------------------------------
已解决，文档中说，验签用的是支付宝公钥，并不是RSA公钥，申请接口的人没有给我支付宝公钥，我一直以为用RSA公钥，我用错了，