Sort XML via attribute value PHP

Question

So I have an XML file that I am trying to loop through in order, according to the attribute, \"order\".

Here is an example:

Answer 1

I wrote a recursive, expanded version that will sort by any number of attributes, in order:

//sort_xml_by_attr($simplexmlobject,array('attr_one','attr_two','attr_three'))

  class SortXML {
    public $xml;
    var $attr;
    function SortXML($xml,$attr) {
      $this->xml = $xml;
      $this->attr = $attr;
    }
    function cmp_attr($a,$b) {
      $a1 = (string)$a->xml[(string)$a->attr];
      $b1 = (string)$b->xml[(string)$b->attr];
      if (is_numeric($a1) && is_numeric($b1)) {
        if (is_float($a1) && is_float($b1)) {
          $a1 = (float)$a1;
          $b1 = (float)$b1;
        } else {
          $a1 = (int)$a1;
          $b1 = (int)$b1;
        }
      }
      if ($a1 == $b1) return 0;
      return ($a1 > $b1) ? +1 : -1;
    }
  }

  function sort_xml_by_attr($xml_obj,$attr) {
    if (count($attr)>1) {
      // break up array by unique values of the first attribute in the list
      $unique_attrs = array();
      foreach ($xml_obj as $i) $unique_attrs[] = (string)$i[$attr[0]];
      $unique_attrs = array_unique($unique_attrs);
      sort($unique_attrs);
      // create an array of arrays who share a unique attribute value
      foreach ($unique_attrs as $i) {
        foreach ($xml_obj as $p) {
          if ($p[$attr[0]] == $i) $xml_arrays[$i][] = $p;
        }
      }
      // remove first element to progress the recursion to the next attribute
      array_shift($attr); 
      $new_array = array();
      // concatenate sorted arrays
      foreach ($xml_arrays as $i) {
        $new_array = array_merge($new_array,sort_xml_by_attr($i,$attr));
      }
      return $new_array;
    } else {
      // create wrapper objects with new comparison function 
      foreach ($xml_obj as $i) $new_obj[] = new SortXML($i,$attr[0]);
      usort($new_obj,array('SortXML','cmp_attr'));
      foreach ($new_obj as $i) $sorted_obj[] = $i->xml;
      return $sorted_obj;
    }
  }