PHP DOMDocument - InsertBefore multiple times

Question

I am a situation where I'd like to add the same content in several locations in an XML file. FYI - first time tackling DOMDocument. Say the xml looks like

<rrd>
  <rra>
    <cdp_prep>
      <ds>
        <value>nan</value>
      </ds>
      <ds>
        <value>nan</value>
      </ds>
      <ds>
        <value>nan</value>
      <ds>
     </cdp_prep>
     <database>
        ...
     </database>
   </rra>
  <rra>
    <cdp_prep>
      <ds>
        <value>nan</value>
      <ds>
      </ds>
        <value>nan</value>
      <ds>
      <ds>
        <value>nan</value>
      </ds>
     </cdp_prep>
     <database>
        ...
     </database>
   </rra>
</rrd>

If i use something like $rrdCDPds = $xRRD->query("/rrd/rra/cdp_prep/ds"); then i would get all the <ds> elements. In this case i would have a length of 6. However, I'm trying to insertBefore on the second <ds> of each <cdp_prep> element. My issue is if i query on "/rrd/rra/cdp_prep", how do i target the insertBefore on the 2nd <ds> element for every <cdp_prep> element?

The xml is not valid .. did you mean to close the ds elements? — Explosion Pills
– Explosion Pills, Commented May 4, 2012 at 22:41
yes sorry. friday afternoon... and beating head on keyboard :) — au_stan
– au_stan, Commented May 7, 2012 at 12:28

Explosion Pills · Accepted Answer · 2012-05-04 22:46:24Z

1

You can use the child axis in XPath to select the second ds child:

/rrd/rra/cdp_prep/child::ds[2]

answered May 4, 2012 at 22:46

Explosion Pills

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Francis Avila · Accepted Answer · 2012-05-05 00:22:48Z

Basic procedure is:

Select the nodes you want to use as insertBefore reference nodes. You can get this using the child axis and a position test: cdp_prep/child::ds[position()=2], which can be abbreviated as cdp_prep/ds[2].
Prepare the nodes you want to insert.
For each matching reference node, clone the node you want to insert and then insert it.

Example:

$dom = new DOMDocument();
$dom->loadXML($xml);
$xp = new DOMXPath($dom);

$newcontent = $dom->createDocumentFragment();
$newcontent->appendChild($dom->createElement('NEWCONTENT'));
$newcontent->appendChild($dom->createTextNode("\n      "));

$DSs = $xp->query('/rrd/rra/cdp_prep/ds[2]');

foreach ($DSs as $ds) {
    $ds->parentNode->insertBefore($newcontent->cloneNode(true), $ds);
}

echo $dom->saveXML();

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