Despite its name, this extension is not designed for generic DOM manipulations, but specifically for XHTML and HTML. Trying to load different types of XML documents will cause them to be altered, unless they are valid HTML documents.
The DOM extension allows you to operate on XML documents through the DOM API with PHP.
Note:
The DOM extension uses UTF-8 encoding. Use utf8_encode() and utf8_decode() to work with texts in ISO-8859-1 encoding or Iconv for other encodings.
Despite its name, this extension is not designed for generic DOM manipulations, but specifically for XHTML and HTML. Trying to load different types of XML documents will cause them to be altered, unless they are valid HTML documents.