Create etrepat/baum Header from XML Defined Hierarchy

hfxHelper.php

<?php

  /**
   * Create headers from an xml string consisting of a hierarchy of nodes with attributes
   * (ex: <header name="A"> <header name="AB" /> <header name="AC"> <header name="AD" /> </header> </header>
   *
   * @param string $content XML string containing hierarchy of nodes
   * @return void
   */
  public function hfxParseContent($content) {
    $xml = new SimpleXMLElement($content);

    $nodeDictionaryHierarchy = array ();
    $nodeDictionaryData = array();

    // parse and evaluate xml hierarchy
    $this->hfxHierarchyParser($xml, $nodeDictionaryHierarchy, $nodeDictionaryData);
    // process evaluated hierarchy and create headers
    $this->hfxHeaderCreator($nodeDictionaryHierarchy, $nodeDictionaryData);
  }

  /**
   * Parse XML and return hierarchy of immediate child. Each node in this hierarchy is represented by it's $uniqueKey
   * (ex returned: array('A' => array('AB', 'AC'), 'AB' => array(), 'AC' => array('AD'), 'AD' =>array() )
   *
   * @param   SimpleXMLElement  $node                       Starting node
   * @param   array             &$nodeDictionaryHierarchy   Array of node identifier with child header identifier
   *                                                        array('A' => array('AB', 'AC'), ...)
   * @param   array             &$nodeDictionaryData        Array of each header with corresponding attributes
   *                                                        array('A' => array('name' => 'A', 'slug' => 'a'), ...)
   * @param   string            $nodeName                   XML node names
   * @param   string            $uniqueKey                  Unique attribute to use to identify each node (internal)
   * @return  void
   */
  private static function hfxHierarchyParser($node, &$nodeDictionaryHierarchy, &$nodeDictionaryData, $nodeName = 'header', $uniqueKey = 'name') {
    // each node needs initialization as an array to hold array of child nodes
    if (array_key_exists("{$node[$uniqueKey]}", $nodeDictionaryHierarchy) === false) {
      $nodeDictionaryHierarchy["{$node[$uniqueKey]}"] = array ();
      $nodeDictionaryData["{$node[$uniqueKey]}"] = self::xml2array($node->attributes());
    }

    // check if node has child nodes
    $nodeNode = $node->$nodeName;
    if (isset($nodeNode)) {
      // push each immediate child to the current node array represented by it's $uniqueKey
      for ($key = 0; ($key < $nodeNode->count()); $key++) {
        $header = $nodeNode[$key];
        if (!in_array("{$node[$uniqueKey]}", $nodeDictionaryHierarchy["{$node[$uniqueKey]}"])) {
          $nodeDictionaryHierarchy["{$node[$uniqueKey]}"][] = "{$header[$uniqueKey]}";
        }
        // recurse through next level down
        self::hfxHierarchyParser($header, $nodeDictionaryHierarchy, $nodeDictionaryData);
      }
    }
  }

  /**
   * Create and link headers from the hierarchy array
   *
   * @param   array $nodeDictionaryHierarchy
   * @param   array $nodeDictionaryData
   * @return  void
   */
  private static function hfxHeaderCreator(&$nodeDictionaryHierarchy, &$nodeDictionaryData) {
    $headersPool = array();
    foreach ($nodeDictionaryHierarchy as $nodeKey => $childNodeKeys) {
      // create header
      if (!array_key_exists($nodeKey, $headersPool)) {
        $nodeData = $nodeDictionaryData[$nodeKey];
        $headersPool[$nodeKey] = Header::create($nodeData);
      }

      // loop through each child of the header
      foreach($childNodeKeys as $childNodeKey) {

        // create child header
        if (!array_key_exists($childNodeKey, $headersPool)) {
          $childNodeData = $nodeDictionaryData[$childNodeKey];
          $headersPool[$childNodeKey] = Header::create($childNodeData);
        }

        // set as child
        $headersPool[$childNodeKey]->makeChildOf($headersPool[$nodeKey]);
      }
    }
  }

  /**
   * Convert SimpleXMLElement to array
   * source: http://stackoverflow.com/questions/7778814/how-to-convert-simplexmlobject-into-php-array
   *
   * @param   SimpleXMLElement $xml
   * @return  array
   */
  public function xml2array($xml) {
    $arr = array();

    foreach ($xml as $element) {
      $tag = $element->getName();
      $e = get_object_vars($element);
      if (!empty($e)) {
        $arr[$tag] = $element instanceof SimpleXMLElement ? xml2array($element) : $e;
      }
      else {
        $arr[$tag] = trim($element);
      }
    }

    return $arr;
  }

run.php

<?    

  $data = '
    <header name="A" slug="a">
      <header name="B" slug="b">

        <header name="C" slug="c">
          <header name="D" slug="d" />
        </header>

      </header>
    </header>
  ';

  $this->hfxParseContent($data);