PHP XML如何创建嵌套节点？

I use php DOMDocument to create and save XML file. here is my code

$doc = new DOMDocument();
$document = $doc->createElement('DOCUMENT');
$document->nodeValue = '';
$doc->appendChild($document);

$order = $doc->createElement('ORDER');
$order->nodeValue = '';
$doc->appendChild($order);

$ele = $doc->createElement('Reportvariable1');
$ele->nodeValue = '';
$doc->appendChild($ele);

$ele = $doc->createElement('Reportvariable1');
$ele->nodeValue = '';
$doc->appendChild($ele);

$ele = $doc->createElement('Reportvariable1');
$ele->nodeValue = '';
$doc->appendChild($ele);

$ele = $doc->createElement('Reportvariable1');
$ele->nodeValue = '';
$doc->appendChild($ele);

$doc->appendChild($ele);
$doc->save('order_xml/Order_.xml');

its Output is simple like this :

<?xml version="1.0"?>
<DOCUMENT></DOCUMENT>
<ORDER></ORDER>
<Reportvariable1></Reportvariable1>
<Reportvariable1></Reportvariable1>
<Reportvariable1></Reportvariable1>
<Reportvariable1></Reportvariable1>

How do I create nested nodes like this ?

<?xml version="1.0"?>
<DOCUMENT>
    <ORDER>
       <Reportvariable1></Reportvariable1>
       <Reportvariable1></Reportvariable1>
       <Reportvariable1></Reportvariable1>
       <Reportvariable1></Reportvariable1>
   </ORDER>
</DOCUMENT>

You use 3 steps to add a new node to the DOM.

1. Create the node using a method of the document object
2. Append the node using appendChild() to the parent (document or element)
3. Optionally set attributes on the element node.

appendChild() returns the node. So you can nest the create* call.

Don't set DOMElement::$nodeValue. It needs special escaping. It is much more secure to create a text node and append it.

$dom = new DOMDocument();
$document = $dom->appendChild(
  $dom->createElement('DOCUMENT')
);
$order = $document->appendChild(
  $dom->createElement('ORDER')
);
for ($i = 1; $i < 5; $i++) {
  $reportVariable = $order->appendChild(
    $dom->createElement('Reportvariable1')
  );
  // add some text content 
  $reportVariable->appendChild(
    $dom->createTextNode('some text content' . $i)
  );
}
$dom->formatOutput = true;
echo $dom->saveXml();

Output:

<?xml version="1.0"?>
<DOCUMENT>
  <ORDER>
    <Reportvariable1>some text content1</Reportvariable1>
    <Reportvariable1>some text content2</Reportvariable1>
    <Reportvariable1>some text content3</Reportvariable1>
    <Reportvariable1>some text content4</Reportvariable1>
  </ORDER>
</DOCUMENT>

Change your code to:-

$doc = new DOMDocument();
    $document = $doc->createElement('DOCUMENT');$document->nodeValue = '';$doc->appendChild($document);
    $order = $doc->createElement('ORDER');$order->nodeValue = '';$document->appendChild($order);

    $ele = $doc->createElement('Reportvariable1');$ele->nodeValue = '';$order->appendChild($ele);
    $ele = $doc->createElement('Reportvariable1');$ele->nodeValue = '';$order->appendChild($ele);
    $ele = $doc->createElement('Reportvariable1');$ele->nodeValue = '';$order->appendChild($ele);
    $ele = $doc->createElement('Reportvariable1');$ele->nodeValue = '';$order->appendChild($ele);
    $doc->save('order_xml/Order_.xml');

You will get the desired output