Exporting defined elements from XML - php

Question

I would like to export (or to keep) the subtags which are with the defined attribute in XML. As I don't know the name of this process, I can't find any relevant information about it on the net. And since it's hard to explain, I decided to put an examples for my issue.
Let's say, I have this XML file:
<results>
<result idSite="1">
<row>
<label>category</label>
<visits>2</visits>
<idsubdatatable>5</idsubdatatable>
<subtable>
<row>
<label>uncategorized</label>
<visits>2</visits>
<idsubdatatable>6</idsubdatatable>
<subtable>
<row>
<label>/index</label>
<visits>2</visits>
<url>http://mysite1.com/category/uncategorized/</url>
</row>
</subtable>
</row>
</subtable>
</row>
<row>
<label>about</label>
<visits>1</visits>
<idsubdatatable>7</idsubdatatable>
<subtable>
<row>
<label>/index</label>
<visits>1</visits>
<url>http://mysite1.com/about/</url>
</row>
</subtable>
</row>
</result>
<result idSite="2">
<row>
<label>/calendar</label>
<visitors>1</visitors>
<url>http://mysite2.com/calendar</url>
</row>
</result>
</results>
And I have to parse the results and keep only the rows which are with a <url> attribute. Like this:
After parsing I have to combine these rows in a new XML file, and the final result must be like this:
<result>
<row>
<label>/index</label>
<visits>2</visits>
<url>http://mysite1.com/category/uncategorized/</url>
</row>
<row>
<label>/index</label>
<visits>1</visits>
<url>http://mysite1.com/about/</url>
</row>
<row>
<label>/calendar</label>
<visitors>1</visitors>
<url>http://mysite2.com/calendar</url>
</row>
</result>
Generally I want to do this process in PHP but it maybe in other languages too.
So, if you have any idea to solve this problem, please comment.

Answer 1

I would use an xpath query to find all url nodes inside row nodes. Then, just append the parent node of each url element you find to a new DomDocument like so:
$xml = '...';
$dom = new DomDocument();
$dom->preserveWhiteSpace = FALSE;
$dom->loadXML($xml);
$new_dom = new DomDocument();
$result = $new_dom->createElement('result');
$new_dom->appendChild($result);
$xpath = new DOMXPath($dom);
$rows = $xpath->query('//row/url');
for ($i=0;$i<$rows->length;$i++) {
$node = $new_dom->importNode($rows->item($i)->parentNode, TRUE);
$result->appendChild($node);
}
$new_dom->formatOutput = TRUE;
echo $new_dom->saveXML();

Answer 2

I'd use simplexml to read as your input, so your parsing would be easy. And then, i'd create a recursive function such as:
function isUrlElement($element){
foreach($element->children() as $children){
if($children->getName() == 'url'){
return true;
}else{
isUrlElement($children);
}
}
}
Now this is far from complete, but you could make it recursive calling it for each children. When this returns true, you'd know you found a node that has URL as a children. Use that $element node to for example add it to an array of simplexmlelements and then just foreach it back into XML.
Does that make sense?