edit

lib/Wechat.php

@@ -133,7 +133,7 @@ class Wechat extends Core
 			# 下单信息
 			$order['time'] = '' . time() . '';
 			$order['order_id'] = $order_id;
-			$order['sign_type'] = 'MD5';
+			$order['sign_type'] = $this->config->GetSignType();
 			unset($order['mch_id']);
 			$this->updateOrderParam($order_id, $order);
 			return $order;

sdk/wechat/WxPay.Config.php

@@ -33,7 +33,7 @@ class WxPayConfig
 	}
 	public function GetSignType()
 	{
-		return "MD5";
+		return "HMAC-SHA256";
 	}
 	public function GetProxy(&$proxyHost, &$proxyPort)
 	{