方法链接和PHP 5.4.x中的新关键字返回错误

Question

I was trying to chain the following code below into 1 line. Purely for experimentation to see if it could be done.

This is the original code, which works:

$dom = new DomDocument();
$dom->loadHtml($html);
$xpath = new DomXPath($dom);

But, when chaining, this returns an error:

$xpath = new DomXPath((new DomDocument())->loadHtml($html));

The error is:

Catchable fatal error: Argument 1 passed to DOMXPath::__construct() must be an instance of DOMDocument, boolean given

If this sort of chaining is allowed in PHP 5.4.x the why does it not work as expected?

Answer 1

The error actually said it just perfeclly: loadHtml returned a Bool (true/false). Check the manual for the return value.

Error: Catchable fatal error: Argument 1 passed to DOMXPath::__construct() must be an instance of DOMDocument, boolean given

Code:

$xpath = new DomXPath((new DomDocument())->loadHtml($html));
//                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//                     Argument 1, that returned a bool.