diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index 4b03409c99d..2db7f65f261 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -8,7 +8,8 @@ Yii Framework 2 Change Log
 - Enh #18826: Add ability to turn the sorting off for a clicked column in GridView with multisort (ditibal)
 - Bug #18646: Remove stale identity data from session if `IdentityInterface::findIdentity()` returns `null` (mikehaertl)
 - Bug #18832: Fix `Inflector::camel2words()` adding extra spaces (brandonkelly)
-
+- Enh #18783: Add support for URI namespaced tags in `XmlResponseFormatter` (WinterSilence, samdark)
+- Enh #18783: Add `XmlResponseFormatter::$objectTagToLowercase` option to lowercase object tags (WinterSilence, samdark)
 
 2.0.43 August 09, 2021
 ----------------------
diff --git a/framework/web/XmlResponseFormatter.php b/framework/web/XmlResponseFormatter.php
index 40e9776bc72..f55d5da3f04 100644
--- a/framework/web/XmlResponseFormatter.php
+++ b/framework/web/XmlResponseFormatter.php
@@ -10,7 +10,6 @@
 use DOMDocument;
 use DOMElement;
 use DOMException;
-use DOMText;
 use yii\base\Arrayable;
 use yii\base\Component;
 use yii\helpers\StringHelper;
@@ -38,7 +37,10 @@ class XmlResponseFormatter extends Component implements ResponseFormatterInterfa
      */
     public $encoding;
     /**
-     * @var string the name of the root element. If set to false, null or is empty then no root tag should be added.
+     * @var string|string[]|false the name of the root element. If set to false, null or is empty then no root tag
+     * should be added.
+     *
+     * Since 2.0.43 URI namespace could be specified by passing `[namespace, tag name]` array.
      */
     public $rootTag = 'response';
     /**
@@ -52,14 +54,26 @@ class XmlResponseFormatter extends Component implements ResponseFormatterInterfa
      */
     public $useTraversableAsArray = true;
     /**
-     * @var bool if object tags should be added
+     * @var bool if object class names should be used as tag names
      * @since 2.0.11
      */
     public $useObjectTags = true;
+    /**
+     * @var bool if true, converts object tags to lowercase, `$useObjectTags` must be enabled
+     * @since 2.0.43
+     */
+    public $objectTagToLowercase = false;
+
+    /**
+     * @var DOMDocument the XML document, serves as the root of the document tree
+     * @since 2.0.43
+     */
+    protected $dom;
 
 
     /**
      * Formats the specified response.
+     *
      * @param Response $response the response to be formatted.
      */
     public function format($response)
@@ -70,21 +84,27 @@ public function format($response)
         }
         $response->getHeaders()->set('Content-Type', $this->contentType);
         if ($response->data !== null) {
-            $dom = new DOMDocument($this->version, $charset);
+            $this->dom = new DOMDocument($this->version, $charset);
             if (!empty($this->rootTag)) {
-                $root = new DOMElement($this->rootTag);
-                $dom->appendChild($root);
+                if (is_array($this->rootTag)) {
+                    $root = $this->dom->createElementNS($this->rootTag[0], $this->rootTag[1]);
+                } else {
+                    $root = $this->dom->createElement($this->rootTag);
+                }
+                $this->dom->appendChild($root);
                 $this->buildXml($root, $response->data);
             } else {
-                $this->buildXml($dom, $response->data);
+                $this->buildXml($this->dom, $response->data);
             }
-            $response->content = $dom->saveXML();
+            $response->content = $this->dom->saveXML();
         }
     }
 
     /**
-     * @param DOMElement $element
-     * @param mixed $data
+     * Recursively adds data to XML document.
+     *
+     * @param DOMElement|DOMDocument $element current element
+     * @param mixed $data content of the current element
      */
     protected function buildXml($element, $data)
     {
@@ -95,18 +115,22 @@ protected function buildXml($element, $data)
                 if (is_int($name) && is_object($value)) {
                     $this->buildXml($element, $value);
                 } elseif (is_array($value) || is_object($value)) {
-                    $child = new DOMElement($this->getValidXmlElementName($name));
+                    $child = $this->dom->createElement($this->getValidXmlElementName($name));
                     $element->appendChild($child);
                     $this->buildXml($child, $value);
                 } else {
-                    $child = new DOMElement($this->getValidXmlElementName($name));
+                    $child = $this->dom->createElement($this->getValidXmlElementName($name));
+                    $child->appendChild($this->dom->createTextNode($this->formatScalarValue($value)));
                     $element->appendChild($child);
-                    $child->appendChild(new DOMText($this->formatScalarValue($value)));
                 }
             }
         } elseif (is_object($data)) {
             if ($this->useObjectTags) {
-                $child = new DOMElement(StringHelper::basename(get_class($data)));
+                $name = StringHelper::basename(get_class($data));
+                if ($this->objectTagToLowercase) {
+                    $name = strtolower($name);
+                }
+                $child = $this->dom->createElement($name);
                 $element->appendChild($child);
             } else {
                 $child = $element;
@@ -121,7 +145,7 @@ protected function buildXml($element, $data)
                 $this->buildXml($child, $array);
             }
         } else {
-            $element->appendChild(new DOMText($this->formatScalarValue($data)));
+            $element->appendChild($this->dom->createTextNode($this->formatScalarValue($data)));
         }
     }
 
@@ -152,7 +176,7 @@ protected function formatScalarValue($value)
      *
      * Falls back to [[itemTag]] otherwise.
      *
-     * @param mixed $name
+     * @param mixed $name the original name
      * @return string
      * @since 2.0.12
      */
@@ -168,7 +192,7 @@ protected function getValidXmlElementName($name)
     /**
      * Checks if name is valid to be used in XML.
      *
-     * @param mixed $name
+     * @param mixed $name the name to test
      * @return bool
      * @see http://stackoverflow.com/questions/2519845/how-to-check-if-string-is-a-valid-xml-element-name/2519943#2519943
      * @since 2.0.12
@@ -176,8 +200,7 @@ protected function getValidXmlElementName($name)
     protected function isValidXmlName($name)
     {
         try {
-            new DOMElement($name);
-            return true;
+            return $this->dom->createElement($name) !== false;
         } catch (DOMException $e) {
             return false;
         }
diff --git a/tests/framework/web/XmlResponseFormatterTest.php b/tests/framework/web/XmlResponseFormatterTest.php
index 947c50af004..20a63f81769 100644
--- a/tests/framework/web/XmlResponseFormatterTest.php
+++ b/tests/framework/web/XmlResponseFormatterTest.php
@@ -46,6 +46,7 @@ public function formatScalarDataProvider()
             [true, "<response>true</response>\n"],
             [false, "<response>false</response>\n"],
             ['<>', "<response>&lt;&gt;</response>\n"],
+            ['a&b', "<response>a&amp;b</response>\n"],
         ]);
     }
 
@@ -58,6 +59,10 @@ public function formatArrayDataProvider()
                 'a' => 1,
                 'b' => 'abc',
             ], "<response><a>1</a><b>abc</b></response>\n"],
+            [
+                ['image:loc' => 'url'],
+                "<response><image:loc>url</image:loc></response>\n"
+            ],
             [[
                 1,
                 'abc',
@@ -79,7 +84,7 @@ public function formatArrayDataProvider()
                 'b:c' => 'b:c',
                 'a b c' => 'a b c',
                 'äøñ' => 'äøñ',
-            ], "<response><item>1</item><item>2015-06-18</item><item>b:c</item><item>a b c</item><äøñ>äøñ</äøñ></response>\n"],
+            ], "<response><item>1</item><item>2015-06-18</item><b:c>b:c</b:c><item>a b c</item><äøñ>äøñ</äøñ></response>\n"],
         ]);
     }
 
@@ -162,4 +167,13 @@ public function testNoObjectTags()
         $formatter->format($this->response);
         $this->assertEquals($this->xmlHead . "<response><id>123</id><title>abc</title></response>\n", $this->response->content);
     }
+
+    public function testObjectTagToLowercase()
+    {
+        $formatter = $this->getFormatterInstance(['objectTagToLowercase' => true]);
+
+        $this->response->data = new Post(123, 'abc');
+        $formatter->format($this->response);
+        $this->assertEquals($this->xmlHead . "<response><post><id>123</id><title>abc</title></post></response>\n", $this->response->content);
+    }
 }