Order SimpleXMLElement by element

Question

Hi everyone

I need to order a SimpleXMLElement by a node called padre like this.

$xml = new SimpleXMLElement('sitemap.xml',null,true); sort($xml, "padre" );
foreach($xml as $url ) { echo "loc}' title='".rescue_name($url->loc)."'>".rescue_name($url->loc)." {$url->padre}
";

  }

I don't know why is not working please let me know what is my error. Thanks in advance