Php xml operations

For XML operations in PHP, I used php to generate the following xml: PHPcode $ xml & lt ;? Xmlversion & quot; 1.0 & quot; encoding & quot; UTF-8 & quot ;? & Gt;. & quot; rn & quot; $ xml. & lt; user & gt;. & quot; rn & quot; $ xml. & quot php xml operation problems
I use php to generate xml as follows:

PHP code

  $xml = '
  '."\r\n";$xml .= '
  
   '."\r\n";$xml .= "\t".'
   
    '.www.163.com.'
   '."\r\n";foreach (array(1,2,3) as $value){   $xml .= "\t".'
   
    '.$value.'
   '."\r\n";}$xml .= '
  '."\r\n";$sxe = new SimpleXMLElement($xml);$sxe->asXML(APPPATH.'user.xml');

The user. xml file is generated. now I want to add one:
Li Si
How can I add it? I followed "\ t", and I followed "\ r \ n "?

Thanks ~~

------ Solution --------------------

PHP code

$ Sxe = new SimpleXMLElement ($ xml); $ sxe-> addChild ('username', 'Lee si'); $ sxe-> asXML (APPPATH. 'user. XML ');