初始化项目：添加后端代码、ThinkPHP框架、前端资源

addons/epay/library/OrderException.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace addons\epay\library;
+
+use think\Exception;
+
+class OrderException extends Exception
+{
+    public function __construct($message = "", $code = 0, $data = [])
+    {
+        $this->message = $message;
+        $this->code = $code;
+        $this->data = $data;
+    }
+
+}