Only explicitly set encoding if not provided by the XML parser

Author: nielsdos

ext/dom/tests/modern/xml/XMLDocument_fromString_04.phpt

@@ -0,0 +1,16 @@
+--TEST--
+DOM\XMLDocument::createFromString 04
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$dom = DOM\XMLDocument::createFromString('<?xml version="1.0" encoding="Windows-1251"?><container/>');
+var_dump($dom->encoding);
+echo $dom->saveXML();
+
+?>
+--EXPECT--
+string(12) "Windows-1251"
+<?xml version="1.0" encoding="Windows-1251"?>
+<container/>

ext/dom/xml_document.c

@@ -228,10 +228,12 @@ static void load_from_helper(INTERNAL_FUNCTION_PARAMETERS, int mode)
 		}
 		RETURN_THROWS();
 	}
-	if (override_encoding) {
-		lxml_doc->encoding = xmlStrdup((const xmlChar *) override_encoding);
-	} else {
-		lxml_doc->encoding = xmlStrdup((const xmlChar *) "UTF-8");
+	if (lxml_doc->encoding == NULL) {
+		if (override_encoding) {
+			lxml_doc->encoding = xmlStrdup((const xmlChar *) override_encoding);
+		} else {
+			lxml_doc->encoding = xmlStrdup((const xmlChar *) "UTF-8");
+		}
 	}
 	dom_object *intern = php_dom_instantiate_object_helper(
 		return_value,