added customize <?xml?>

Author: darkfriend

readme.md

@@ -35,6 +35,7 @@ echo \darkfriend\helpers\Xml::encode($array);
 #### Result encode
 
 ```xml
+<?xml version="1.0" encoding="utf-8"?>
 <root>
     <bar>value bar</bar>
     <foo>value foo</foo>
@@ -90,4 +91,91 @@ Array
                 )
         )
 )
+```
+
+### Custom \<?xml \?> attributes
+
+```php
+$array = array(
+    'bar' => 'value bar',
+    'foo' => 'value foo',
+    'der' => array(
+        '@cdata' => 'this is long text',
+        '@attributes' => array(
+            'at1' => 'at1val',
+            'at2' => 'at2val',
+        ),
+    ),
+    'qpo' => array(
+        'sub1' => array('sub2'=>'val')
+    )
+);
+
+echo \darkfriend\helpers\Xml::encode(
+    $array,
+    [
+        'header' => [
+            'version' => 1.0,
+            'encoding' => 'utf-8',
+        ],
+    ]
+);
+```
+
+```xml
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+    <bar>value bar</bar>
+    <foo>value foo</foo>
+    <der at1="at1val" at2="at2val"><![CDATA[this is long text]]></der>
+    <qpo>
+        <sub1>
+            <sub2>val</sub2>
+        </sub1>
+    </qpo>
+</root>
+```
+
+### Custom root element
+
+```php
+$array = array(
+    'bar' => 'value bar',
+    'foo' => 'value foo',
+    'der' => array(
+        '@cdata' => 'this is long text',
+        '@attributes' => array(
+            'at1' => 'at1val',
+            'at2' => 'at2val',
+        ),
+    ),
+    'qpo' => array(
+        'sub1' => array('sub2'=>'val')
+    )
+);
+
+echo \darkfriend\helpers\Xml::encode(
+    $array,
+    [
+        'root' => '<response/>',
+        'header' => [
+            'version' => 1.0,
+            'encoding' => 'utf-8',
+        ],
+    ]
+);
+```
+
+```xml
+<?xml version="1.0" encoding="utf-8"?>
+<response>
+    <bar>value bar</bar>
+    <foo>value foo</foo>
+    <der at1="at1val" at2="at2val"><![CDATA[this is long text]]></der>
+    <qpo>
+        <sub1>
+            <sub2>val</sub2>
+        </sub1>
+    </qpo>
+</response>
 ```

src/Xml.php

@@ -18,6 +18,7 @@ class Xml
      * @param array $params = [
      *     'root' => '<root/>',
      *     'exception' => false,
+     *     'header' => false,
      * ]
      * @return string
      * @throws XmlException
@@ -29,8 +30,13 @@ public static function encode($data, $params = array())
         if(empty($params['root'])) {
             $params['root'] = self::$root;
         }
+        if(!isset($params['header'])) {
+            $params['header'] = false;
+        }
 
-        $xml = new SimpleXMLElement($params['root']);
+        $xml = new SimpleXMLElement(
+            self::getHeader($params['header']).$params['root']
+        );
         $xml = self::generateXml($xml, $data);
 
         if(!static::checkException($params)) {
@@ -40,6 +46,34 @@ public static function encode($data, $params = array())
         return $xml->asXML();
     }
 
+    /**
+     * @param array $params header attributes
+     * @return string
+     * @since 1.0.1
+     */
+    public static function getHeader($params = array())
+    {
+        if(!$params) return '';
+        if(!is_array($params)) {
+            $params = array();
+        }
+
+        $params = array_merge(
+            array(
+                'version' => '1.0',
+                'encoding' => 'utf-8',
+            ),
+            $params
+        );
+
+        $attr = array();
+        foreach ($params as $attrKey=>$attrVal) {
+            $attr[] = "$attrKey=\"$attrVal\"";
+        }
+
+        return '<?xml '.implode(' ', $attr).'?>';
+    }
+
     /**
      * @param SimpleXMLElement $xml
      * @param mixed $data