reordering array attributes then save back to XML in php

Question

I have this XML:

  
    
  
  
    
  <         


        

Answer 1

In XML order of nodes in same level is doesn't matter then you can't do this by theory, by practice user other library.

Answer 2

Numerical id order is maintained and made consecutive:

$objXML = new SimpleXMLElement(XML_FILE_NAME, null, true);
$picture = $objXML->xpath('picture');
usort($picture, create_function('$a,$b', 'return (string)$a["id"] - (string)$b["id"];'));
foreach ($pictures as $index => $node) $node["id"] = $index;