php domdocument exception loadHTMLFile

I am having a strange behavior in my script. That has me confused

Script 1.

$dom = new DOMDocument();
$dom->loadHTMLFile("html/signinform.html");//loads file here
$form = $dom->getElementsByTagName("form")->item(0)开发者_JAVA技巧;
$div = $dom->createElement("div");
$dom->appendChild($div)->appendChild($form);
echo $dom->saveHTML();

Script 2.

$dom = new DOMDocument();
$div = $dom->createElement("div");
$dom->loadHTMLFile("html/signinform.html");//loads file here
$form = $dom->getElementsByTagName("form")->item(0);
$dom->appendChild($div)->appendChild($form);
echo $dom->saveHTML();

Script 1 works without problem. It shows the form. However Script 2 throws the following error: Fatal error: Uncaught exception 'DOMException' with message 'Wrong Document Error' in C:\Users

Could someone explain to me why the mere changing of position of the loadHTMLFile function results in such error? Thanks

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You have added an element to the DOM (div) and then attempted to load a file to be parsed and its DOM structure used.

Load the file first if you intend to use one.

---

For DOM manipulation you do not need to insert an already existing element so doing something like this: $dom->appendChild($form) only reinserts the same form element, when you pull an element using $dom->getElementsByTag("form")->item(0) it becomes it's own DOM object which you can reference directly and append to. A proper example would be:

$dom = new DOMDocument();
$dom->loadHTMLFile("assets/dom_document-form.html");
$div = $dom->createElement("div");
$form = $dom->getElementsByTagName("form")->item(0);
$form->appendChild($div);
echo $dom->saveHTML();

One should append directly to the object they pulled from the DOM instead and load the document first.
To help aid your initial questions too:

• Append directly to element that you pulled as it references the object.
• new DOMDocument can be used to create multiple documents.
• using DOMDocument::createElement before loadHTMLFile creates 2 DOMDocuments.
• Using DomDocument::createDocumentFragment acts the same and creates it's own DOM.

If you would like to keep your code the same and create two DomDocuments then you should use DomDocument::importNode, an example of this would be:

$dom = new DOMDocument();
$div = $dom->createElement("div");
$dom->loadHTMLFile("assets/dom_document-form.html");
$node = $dom->importNode($div);
$form = $dom->getElementsByTagName("form")->item(0);
$form->appendChild($node);
echo $dom->saveHTML();