dom_helper.php

<?php

if(  !function_exists('load_dom')  ) {
// Loads HTML properly with encoding
function load_dom($html) {
  $dom = new DOMDocument('1.0', 'utf-8');
  libxml_use_internal_errors(true); // disable printing parse warnings
  $dom->loadHTML(mb_convert_encoding($html, 'HTML-ENTITIES', 'UTF-8')); // unicode support
  libxml_clear_errors();            // "
  return $dom;
}
}

if(  !function_exists('fragment_to_dom')  ) {
// HTML fragment to DOM
// Returns element reference (for passed selector) for fragment
// element->ownerDocument for containing DOMDocument
function fragment_to_dom($html, $selector = false) {
  $dom = load_dom($html);
  // Element reference for fragment
  if($selector) {
    $xpath  = new DOMXpath($dom);
    $result = $xpath->query($selector);
    $el     = $result->item(0);
  } else {
    $el  = $dom->getElementsByTagName('body')->item(0);
  }
  
  //$el->documentElement = $dom; // for unknown reasons the element has no documentElement property
  return $el;
}
}

if(  !function_exists('dom_to_fragment')  ) {
// DOM to HTML fragment
function dom_to_fragment($el) {
  $tempDom = new DOMDocument('1.0', 'utf-8');
  $tempImported = $tempDom->importNode($el, true);
  $tempDom->appendChild($tempImported);
  $html = $tempDom->saveHTML();
  return $html;
}
}

if(  !function_exists('dom_sibling_position')  ) {
// Determines position of child node relative to given siblings node
// Returns -1 if node wasn't found between given siblings - 
// which happens with a root element that is no child of another element 
// or when the node isn't a sibling of any of the given siblings.
function dom_sibling_position($el, $el_siblings) {
  for($el_sibling_index = 0; $el_sibling_index <= $el_siblings->length; $el_sibling_index++) {
    $el_sibling = $el_siblings->item($el_sibling_index);
    if($el->isSameNode($el_sibling)) {
      return $el_sibling_index;
    }
  }
  return -1;
}
}

if(  !function_exists('dom_change_tagname')  ) {
// Changes the tag name of a node
// (http://stackoverflow.com/questions/8163298/how-do-i-change-xml-tag-names-with-php)
function dom_change_tagname( DOMElement $oldTag, $newTagName ) {
    $document = $oldTag->ownerDocument;

    $newTag = $document->createElement($newTagName);
    $oldTag->parentNode->replaceChild($newTag, $oldTag);

    foreach ($oldTag->attributes as $attribute) {
        $newTag->setAttribute($attribute->name, $attribute->value);
    }
    foreach (iterator_to_array($oldTag->childNodes) as $child) {
        $newTag->appendChild($oldTag->removeChild($child));
    }
    return $newTag;
}
}