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:

<page>
<talentTrees>
<tree name="Football" order="2">
<tree name="Baseball" order="0">
<tree name="Frisbee" order="1">
</talentTrees>
</page>

My goal is to loop through each "tree" using foreach, but I want to read them in order of the order attribute: Baseball, Frisbee, Football. (0,1,2).

Sorry for poor English, not my first language.

Answer 1

This page gives some great examples which I thin you could use

Answer 2

This should give you what you want:

$string = <<<EOS
<page>
<talentTrees>
<tree name="Football" order="2" />
<tree name="Baseball" order="0" />
<tree name="Frisbee" order="1" />
</talentTrees>
</page>
EOS;

$xml = simplexml_load_string($string);

$trees = $xml->xpath('/page/talentTrees/tree');
function sort_trees($t1, $t2) {
    return strcmp($t1['order'], $t2['order']);
}

usort($trees, 'sort_trees');
var_dump($trees);

$trees are now sorted by the order attribute.

Answer 3

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;
    }
  }

Answer 4

For future reference, here's something you can use to query nodes via XPath and sort the result via XPath as well: SimpleDOM. In this example, I sort all <tree/> nodes by values of the order attribute:

include 'SimpleDOM.php';

$page = simpledom_load_string('<page>
    <talentTrees>
        <tree name="Football" order="2"/>
        <tree name="Baseball" order="0"/>
        <tree name="Frisbee" order="1"/>
    </talentTrees>
</page>');

$nodes = $page->sortedXPath('//tree', '@order');

foreach ($nodes as $node)
{
    echo $node->asXML(), "\n";
}