PHP调用未定义的方法DOMElement

Question

I have wrap class for creating xml file and i dont know how to rewrite add() method to work correctly. Variable SHOPITEM should be parent element, but i dont know how to reach it in add method.

Any advice are welcome

  class Items {

    const XML_VERSION enter code here= '1.0';
    const XML_ENCODING = 'utf-8';
    const SHOP = 'SHOP';

    private $xml, $xmlElement;

    public function __construct() {
        $this->xml = new DOMDocument(self::XML_VERSION, self::XML_ENCODING);
        //$this->xml->preserveWhiteSpace = false;
        $this->xml->formatOutput = true;
        $this->xmlElement = $this->create(self::SHOP);
    }

    public function create($nodeName, $value = null) {
        return $this->xml->createElement($nodeName, $value);
    }

    public function add($object) {
        return $this->xmlElement->appendChild($object);
    }

    public function write() {
        $this->xml->appendChild($this->xmlElement);
        $this->xml->save("test.xml");
    }

}

$items = new Items();
$SHOPITEM = $items->create('SHOPITEM');
$product1 = $items->create('Product1', 'Some value 1');
$product2 = $items->create('Product2', 'Some value 2');

//this wont work
$SHOPITEM->add($product1);

//this works
$items->add($product1);
$items->add($product2);

//this works
$items->add($SHOPITEM);

$items->write();

Answer 1

Your $SHOPITEM, $product1 and $product2 are instances of newly added node (i.e. of DOMElement class) because they are result of the statement

return $this->xml->createElement($nodeName, $value);

So they just do nat have a method add($object) that you want to use on them.