remove node inside node in XML using PHP

Question

I want to remove a specific node from my XML file and seems I missed something in code ! can you help me figure it out , for example I want to delete tag and all of its inner tags .

XML structure :

    <students>
    <student>
     <username>sally</username>
     <subjects>
    <subjects>sub1</subjects>
    <subjects>sub2</subjects>
    <subjects>sub3</subjects>
     </subjects>
    </student>
<student>
     <username>jojo</username>
     <subjects>
    <subjects>sub1</subjects>
    <subjects>sub2</subjects>
    <subjects>sub3</subjects>
 <subjects>sub4</subjects>
 <subjects>sub5</subjects>
     </subjects>
    </student>
    </students>

function :

 public static function delete_subjects($UserName, $fileName) {
        //delete from xml
        $xml = new DOMDocument();
        $xml->load($fileName);

        $users = $xml->getElementsByTagName('student');
        foreach ($users as $user) {
          $username = $user->getElementsByTagName('username')->item(0)->nodeValue;
          if ($username == $UserName) {
                $p=$user->getElementsByTagName('subjects')->item(0);
                $xml->documentElement->removeNode($p);

                break;
            }
        }
        $xml->save($fileName);
    }

call :

delete_subjects('jojo', $fileName);

Answer 1

Instead of $xml->documentElement->removeNode($p); try using $user->removeChild($p);

Edit : or even $p->parentNode->removeChild($p);