PHP简单的html dom，试图获取非对象的属性

Question

I get the next notice when firing a specific function:

Trying to get property of non-object in...

My function:

private function rate($form)
{
    $score = 0;

    $count = $form->find('input')->length;
    $score += ($count >= 2 && $count <= 5) ? INPUT_COUNT_RATE : 0;

    $count = $form->find('textarea')->length;
    $score += $count == 1 ? TEXTAREA_COUNT_RATE : 0;

    return $score;
}

The problematic lines are the lines with the find function.

A var_dump of $form returns:

object(simple_html_dom_node)[1062]...

What could be the problem?

Answer 1

->find() returns either an array of matched nodes, or null. You can't call ->length on find results, because the results are not an object. Try

$nodes = $form->find(...);
$count = count($nodes);