Using recursion to iterate over XML file - php

Question

I am having an issue with a recursive function I am trying to work on. I have an XML file that essentially documents a file/folder structure. These XML nodes (which represent a file/folder) can be N levels deeps. So, I am trying to write a script that iterates over all the nodes and creates entries into a database. For the folders, I have a table structure that has an ID, field_name, and parent_id columns. The parent_id points to the ID of a folder the current folder resides in. If it's at the root level, the ID is 0.
My problem is that I'm not able to accurately keep track of the parent_id, when I get down lover levels, then comes back up. Here is an example of XML, but realize the folders can be any number of levels:
<XML>
<programs>
<program name ="xxx">
<groups>
<group id ="1" name ="yyy">
<folder name = "ggg">
<file name = "ddfdf"/>
<file name = "ddfdf"/>
<folder name = "sub" />
</folder>
<folder name = "sdfsdfs">
<file name = "ddfdf"/>
<folder name = "sub" >
<file name = "ddfdf"/>
</folder>
</folder>
</group>
</groups>
</program>
</programs>
</xml>
Script:
foreach($program as $p){
//creates root folder and returns ID
$id = create_folder($folder);
$rootId = $id;
$groups = $program->groups;
if($p->groups){
foreach($p->groups as $group){
foreach($group as $folder){
process_folder($folder,$id, $rootId);
}
}
}
}
function process_folder(($folder,$id, $rootId){
foreach($folder as $key=>$value){
switch ($key){
case "folder":
//creates folder, then returns the ID of the db record
$parentId = create_folder($folder);
process_folder($value, $parentId, $rootId);
//reset ID but this doesnt seem to work
$parentId = $rootId;
break;
case "file":
break;
}
}
}

Answer 1

This is not a complete solution but it shows how a recursiveIterator might be used to accomplish what you want to do.
$strxml='
<xml>
<programs>
<program name ="xxx">
<groups>
<group id ="1" name ="yyy">
<folder name = "ggg">
<file name = "ddfdf"/>
<file name = "ddfdf"/>
<folder name = "sub" />
</folder>
<folder name = "sdfsdfs">
<file name = "ddfdf"/>
<folder name = "sub" >
<file name = "ddfdf"/>
</folder>
</folder>
</group>
</groups>
</program>
</programs>
</xml>';
class RecursiveDOMIterator implements RecursiveIterator {
private $index;
private $list;
public function __construct(DOMNode $domNode){
$this->index = 0;
$this->list = $domNode->childNodes;
}
public function current(){
return $this->list->item($this->index);
}
public function getChildren(){
return new self( $this->current() );
}
public function hasChildren(){
return $this->current()->hasChildNodes();
}
public function key(){
return $this->index;
}
public function next(){
$this->index++;
}
public function rewind(){
$this->index = 0;
}
public function valid(){
return $this->index < $this->list->length;
}
}
$xml=new DOMDocument;
$xml->loadXML( $strxml );
$rootnode=$xml->getElementsByTagName('programs')->item(0);
$nodeItr=new RecursiveDOMIterator( $rootnode );
$itr=new RecursiveIteratorIterator( $nodeItr, RecursiveIteratorIterator::SELF_FIRST );
foreach( $itr as $node ) {
if( $node->nodeType === XML_ELEMENT_NODE ) {
$id=$node->hasAttribute('id') ? $node->getAttribute('id') : false;
$attr=$node->hasAttribute('name') ? $node->getAttribute('name') : false;
echo $id.' '.$node->nodeName . ' ' . $node->nodeValue. ' ' . $attr .' '.$node->parentNode->tagName . ' ' . '<br />';
}
}
$dom=$rootnode=$itr=$nodeItr=null;

Answer 2

Consider using XSLT to simplify your XML to a one child level format. Then run a simple PHP loop to extract parent id and folder data for database migration. In fact, if using MySQL you can import this exact transformed XML document into database with LoadXML(), should node names match column names.
As information, XSLT is a special-purpose, declarative programming language (same type as SQL) used to re-structure XML documents to various structures for end use needs. Like all general purpose languages including C#, Java, Python, Perl, VB, PHP maintains an XSLT processor. Below is an XSLT script (which you can add to for each nest in XML document) and PHP script (to transform and iterate through output).
XSLT Script (save as .xsl or .xslt)
<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output version="1.0" encoding="UTF-8" indent="yes" />
<xsl:strip-space elements="*"/>
<xsl:template match="/">
<root>
<xsl:apply-templates select="*"/>
</root>
</xsl:template>
<xsl:template match="folder" name="foldertemplate">
<row>
<parent_id>0</parent_id>
<field_name><xsl:value-of select="#name"/></field_name>
</row>
<!-- ADD LEVELS FOR EACH NEST IN XML DOCUMENT -->
<row>
<parent_id><xsl:value-of select="#name"/></parent_id>
<field_name><xsl:value-of select="folder/#name"/></field_name>
</row>
<!-- EXAMPLE NEXT LEVEL -->
<!-- <row> -->
<!-- <parent_id><xsl:value-of select="folder/#name"/></parent_id> -->
<!-- <field_name><xsl:value-of select="folder/folder/#name"/></field_name> -->
<!-- </row> -->
</xsl:template>
</xsl:transform>
TRANSFORMED XML OUTPUT (easier to parse and iterate over)
<?xml version="1.0" encoding="UTF-8"?>
<root>
<row>
<parent_id>0</parent_id>
<field_name>ggg</field_name>
</row>
<row>
<parent_id>ggg</parent_id>
<field_name>sub</field_name>
</row>
<row>
<parent_id>0</parent_id>
<field_name>sdfsdfs</field_name>
</row>
<row>
<parent_id>sdfsdfs</parent_id>
<field_name>sub</field_name>
</row>
</root>
PHP Script (to transform and loop through output)
// Set current directory
$cd = dirname(__FILE__);
// Load the XML source and XSLT file
$doc = new DOMDocument();
$doc->load($cd.'/Input.xml');
$xsl = new DOMDocument;
$xsl->load($cd.'/XSLTScript.xsl');
// Configure the transformer
$proc = new XSLTProcessor;
$proc->importStyleSheet($xsl);
// Transform XML source
$newXml = $proc->transformToXML($doc);
// Save output to file
$xmlfile = $cd.'/Output.xml';
file_put_contents($xmlfile, $newXml);
// Load new XML with SimpleXML
$newdoc = simplexml_load_file($cd.'/Output.xml');
$data = [];
$node = $newdoc->xpath('//row');
$parents = $newdoc->xpath('//row/parent_id');
$folders = $newdoc->xpath('//row/field_name');
// Loop through folder names and parent
for($i=0; $i < sizeof($node); $i++) {
echo 'parent: '.$parents[$i]. ' folder: ' . $folders[$i]."\n";
}
#parent: 0 folder: ggg
#parent: ggg folder: sub
#parent: 0 folder: sdfsdfs
#parent: sdfsdfs folder: sub