Using DOMXPath to replace a node while maintaining its position ...

Question

Ok, so I had this neat little idea the other night to create a helper class for DOMDOCUMENT that mimics, to some extent, jQuery's ability to manipulate the DOM of an HTML or XML-based string. Instead of css selectors, XPath is used. For example:

$Xml->load($source)
    ->path('//root/items')
    ->each(function($Context)
    {
        echo $Context->nodeValue;
    });

This would invoke a callback function on every resulting node. Unfortunately, PHP version < 5.3.x doesn't support lambda functions or closures, so I'm forced to do something a bit more like this for the time being:

$Xml->load($source)
    ->path('//root/items')
    ->walk('printValue', 'param1', 'param2');

Everything is working great at the moment and I think this project would be useful to a lot of people, but I'm stuck with one of the functions. I am attempting to mimic jQuery's 'replace' method. Using the following code, I can accomplish this quite easily by applying the following method:

$Xml->load($source)
    ->path('//root/items')
    ->replace($Xml->createElement('foo', 'bar')); // can be an object, string or XPath pattern

The code behind this method is:

public function replace($Content)
{
 foreach($this->results as $Element)
 {
  $Element->parentNode->appendChild($Content->cloneNode(true));
  $Element->parentNode->removeChild($Element);
 }

 return $this;
}

Now, this works. It replaces every resulting element with a cloned version of $Content. The problem is that it adds them to the bottom of the parent node's list of children. The question is, how do I clone this element to replace other elements, while still retaining the original position in the DOM?

I was thinking about reverse-engineering the node I was to replace. Basically, copying over values, attributes and element name from $Content, but I am unable to change the actual element name of the target element.

Reflection could be a possibility, but there's gotta be an easier way to do this.

Anybody?

Answer 1

Lookup if $element has a nextsibbling prior to removing if so do an insertBefore that next sibling otherwise simply append.

public function replace($Content)
{
        foreach($this->results as $Element)
        {
             if ($Element->nextSibling) {
        $NextSiblingReference = $Element->nextSibling;
        $Element->parentNode->insertBefore($Content->cloneNode(true),$NextSiblingReference);
       }
       else {
        $Element->parentNode->appendChild($Content->cloneNode(true)); 
       }
                $Element->parentNode->removeChild($Element);
        }

        return $this;
}

Totally untested though.

Or as AnthonyWJones suggested replaceChild , big oomph how did i miss that moment :)

Answer 2

Use replaceChild instead of appendChild/removeChild.