Referencing to DOMDocument method from DOMElement

Question

I have written below classes to make certain DOM operations easier. I want the Easy_Dom_Element's functions to be able to accept both a string and an element as input though. To do that I have to access DOMDocument's createElement method. The call to Easy_Dom::toElement works fine, but $this within that method points to the Easy_Dom_Element instead of Easy_Dom itself. I've tried a static call to createElement like so: Easy_Dom::createElement($element) but for some reason that is not allowed.

class Easy_Dom extends DOMDocument{

    /*function __construct(){
        $this->registerNodeClass('DOMElement', 'Easy_Dom_Element');
    }*/

    //Gets the first element by tag name
    function getElement($tagName){
        return $this->getElementsByTagName($tagName)->item(0);
    }

    //Creates DOMElement from string if needed
    function toElement($element){
        if(is_string($element))$element = $this->createElement($element);
        return $element;
    }
}

class Easy_Dom_Element extends DOMElement{
    function prependChildEl($element){
        $element = Easy_Dom::toElement($element);
        $this->insertBefore($element, $this->firstChild);
        return $element;
    }

    function appendChildEl($element){
        $element = Easy_Dom::toElement($element);
        $this->appendChild($element);
        return $element;
    }
}

$_testxml = new Easy_Dom('1.0', 'ISO-8859-1');
$_testxml->registerNodeClass('DOMElement', 'Easy_Dom_Element');

//load defaults
$_testxml->load('default.xml');

//test above classes
$test = $_testxml->getElement('general_title');
$test->appendChildEl('test');
echo $test->nodeValue;
echo $_testxml->saveXML();

Answer 1

Just when I was about to give up on this I finally figured it out, it turns out the answer was really simple.

Just reference the DOMElement's DOMDocument using the ownerDocument property like this:

$DOMDocumentFunctionResult = $this->ownerDocument->DOMDocumentFunction();

So in my example:

class Easy_Dom extends DOMDocument{

    /*function __construct(){
        $this->registerNodeClass('DOMElement', 'Easy_Dom_Element');
    }*/

    //Gets the first element by tag name
    function getElement($tagName){
        return $this->getElementsByTagName($tagName)->item(0);
    }

    //Creates DOMElement from string if needed
    function toElement($element){
        if(is_string($element))$element = $this->createElement($element);
        return $element;
    }
}

class Easy_Dom_Element extends DOMElement{
    function prependChildEl($element){
        $element = $this->ownerDocument->toElement($element);
        $this->insertBefore($element, $this->firstChild);
        return $element;
    }

    function appendChildEl($element){
        $element = $this->ownerDocument->toElement($element);
        $this->appendChild($element);
        return $element;
    }
}