PHP: Using simplexml to loop through all levels of an XML file

Question

I have a function which uses simplexml to return the first level of nodes in an XML file and write it into an unordered list:

function printAssetMap() {
    $xml = simplexml_load_file(X_ASSETS);
    $assets = $xml->asset;
    $html = '<ul>'."\n";
    foreach ($assets as $asset) {
        $html .= '<li id="asset'.$asset->asset_assetid.'"><ins>&nbsp;</ins><a href="#">'.$asset->asset_name.' ['.$asset->asset_assetid.']</a></li>'."\n";
    }//end foreach
    $html .= '</ul>'."\n";
    return $html;
}// printAssetMap()

XML I am using, that has nested nodes:

<?xml version="1.0"?>
<assets>
  <asset>
    <asset_name>Home</asset_name>
    <asset_url>/home</asset_url>
    <asset_assetid>1</asset_assetid>
  </asset>
  <asset>
    <asset_name>Projects</asset_name>
    <asset_url>/projects</asset_url>
    <asset_assetid>2</asset_assetid>
    <asset>
      <asset_name>Portfolio</asset_name>
      <asset_url>/projects/portfolio</asset_url>
      <asset_assetid>3</asset_assetid>
    </asset>
    <asset>
      <asset_name>Current Jobs</asset_name>
      <asset_url>/projects/current-jobs</asset_url>
      <asset_assetid>4</asset_assetid>
    </asset>
  </asset>
</assets>

Now, I am starting to add child nodes of the nodes that I am currently returning. Is there a way to loop through ALL levels of child nodes in an xml file, even if I don't know how many levels there are, and add those to my list?

Answer 1

you need to use a recursive function. here is an example that outputs an array from XML. It is from the PHP docs - http://www.php.net/manual/en/ref.simplexml.php. You can amend this to output a list.

<?php 
function XMLToArray($xml) 
{ 
  if ($xml instanceof SimpleXMLElement) { 
    $children = $xml->children(); 
    $return = null; 
  } 

  foreach ($children as $element => $value) { 
    if ($value instanceof SimpleXMLElement) { 
      $values = (array)$value->children(); 

      if (count($values) > 0) { 
        $return[$element] = XMLToArray($value); 
      } else { 
        if (!isset($return[$element])) { 
          $return[$element] = (string)$value; 
        } else { 
          if (!is_array($return[$element])) { 
            $return[$element] = array($return[$element], (string)$value); 
          } else { 
            $return[$element][] = (string)$value; 
          } 
        } 
      } 
    } 
  } 

  if (is_array($return)) { 
    return $return; 
  } else { 
    return $false; 
  } 
} 
?>

Answer 2

So basically what you need to do is a function that takes each <asset/> child of current node, builds the HTML then checks if the current node has <asset/> children of its own and keeps recursing deeper down the tree.

Here's how you can do it:

function printAssetMap()
{
    return printAssets(simplexml_load_file(X_ASSETS));
}

function printAssets(SimpleXMLElement $parent)
{
    $html = "<ul>\n";
    foreach ($parent->asset as $asset)
    {
        $html .= printAsset($asset);
    }
    $html .= "</ul>\n";

    return $html;
}

function printAsset(SimpleXMLElement $asset)
{
    $html = '<li id="asset'.$asset->asset_assetid.'"><ins>&nbsp;</ins><a href="#">'.$asset->asset_name.' ['.$asset->asset_assetid.']</a>';

    if (isset($asset->asset))
    {
        // has <asset/> children
        $html .= printAssets($asset);
    }

    $html .= "</li>\n";

    return $html;
}

By the way, I would expect a function named "printX" to actually print or echo something, rather than return it. Perhaps you should name those functions "buildX" ?