无法弄清楚如何确定SimpleXML节点是否为空

Question

So I have this code:

foreach ($xml->PrintQuestion as $PrintQuestion) {

     //if hint doesn't exist, store question id
     if (!$PrintQuestion->content->multichoice->feedback->hint->Passage) {

         fwrite($fp, "<contentid filename=\"$value\">" . $PrintQuestion->attributes()->id . "</contentid>");

     }

}

Basically, I'm trying to save IDs to an XML file if the Passage node exists, but it seems to be storing every ID whether nodes exist within Passage or not.

Answer 1

What happens if you use empty()

if( empty($PrintQuestion->content->multichoice->feedback->hint->Passage) ) {

    fwrite($fp, "<contentid filename=\"$value\">" . $PrintQuestion->attributes()->id . "</contentid>");      

}