调整xml生成方法，是用PHP内置的SimpleXMLElement对象进行编码

Library/Think/Transform/Driver/Xml.php

@@ -21,7 +21,6 @@ class Xml{
         'root_attr' => [],      //根节点属性
         'item_name' => 'item',  //数字节点转换的名称
         'item_key'  => 'id',    //数字节点转换的属性名
-        'encoding'  => 'utf-8', //字符集编码
     ];
 
     /**
@@ -34,29 +33,31 @@ class Xml{
         //初始化配置
         $config = array_merge($this->config, $config);
 
-        if(is_array($config['root_attr'] && !empty($config['root_attr']))){
+        //创建XML对象
-            $attr = [];
+        $xml = new \SimpleXMLElement("<{$config['root_name']}></{$config['root_name']}>");
-            foreach ($config['root_attr'] as $key => $value) {
+        self::data2xml($xml, $data, $config['item_name'], $config['item_key']);
-                $attr[] = "{$key}=\"{$value}\"";
+        return $xml->asXML();
-            }
-            $attr = implode(' ', $attr);
-        }
-        $attr  = empty($attr) ? '' : " {$attr}";
-        $xml   = "<?xml version=\"1.0\" encoding=\"{$config['encoding']}\"?>";
-        $xml  .= "<{$config['root_name']}{$attr}>";
-        $xml  .= self::data2xml($data, $config['item_name'], $config['item_key']);
-        $xml  .= "</{$config['root_name']}>";
-        return $xml;
     }
 
-    public function decode($data, $assoc = true, array $config = []){
+    /**
+     * 解码XML数据
+     * @param  string  $str    XML字符串
+     * @param  boolean $assoc  是否转换为数组
+     * @param  array   $config 数据配置项
+     * @return string          解码后的XML数据
+     */
+    public function decode($str, $assoc = true, array $config = []){
         //初始化配置
         $config = array_merge($this->config, $config);
 
         //创建XML对象
-        $xml  = new SimpleXMLElement($data);
+        $xml = new \SimpleXMLElement($str);
-        self::xml2data($xml, $data, $config['item_name'], $config['item_key']);
+        if($assoc){
-        return $data;
+            self::xml2data($xml, $data, $config['item_name'], $config['item_key']);
+            return $data;
+        }
+        
+        return $xml;
     }
 
     /**
@@ -68,18 +69,25 @@ class Xml{
      * @param  string $id   数字索引key转换为的属性名
      * @return string
      */
-    static public function data2xml($data, $item = 'item', $id = 'id') {
+    static public function data2xml(SimpleXMLElement $xml, $data, $item = 'item', $id = 'id') {
-        $xml = $attr = '';
+        foreach ($data as $key => $value) {
-        foreach ($data as $key => $val) {
+            //指定默认的数字key
             if(is_numeric($key)){
-                $id && $attr = " {$id}=\"{$key}\"";
+                $id && $val = $key;
                 $key = $item;
             }
-            $xml .= "<{$key}{$attr}>";
+
-            $xml .= (is_array($val) || is_object($val)) ? self::data2xml($val, $item, $id) : $val;
+            //添加子元素
-            $xml .= "</{$key}>";
+            if(is_array($value) || is_object($value)){
+                $child = $xml->addChild($key);
+                self::data2xml($child, $value, $item, $id);
+            } else {
+                $child = $xml->addChild($key, $value);
+            }
+
+            //记录原来的key
+            isset($val) && $child->addAttribute($id, $val);
         }
-        return $xml;
     }
 
     /**
@@ -92,18 +100,17 @@ class Xml{
      * @param  string           $id   数字索引key转换为的属性名
      */
     static public function xml2data(SimpleXMLElement $xml, &$data, $item = 'item', $id = 'id'){
-        foreach ($xml as $items) {
+        foreach ($xml->children() as $items) {
             $key  = $items->getName();
             $attr = $items->attributes();
             if($key == $item && isset($attr[$id])){
                 $key = strval($attr[$id]);
             }
 
-            $child = $items->children();
+            if($items->count()){
-            if(empty($child)){
+                self::xml2data($items, $val);
-                $val = strval($items);
             } else {
-                self::xml2data($child, $val);
+                $val = strval($items);
             }
 
             $data[$key] = $val;