Answer by Tobias for PHP - Get only certain data from XML, not whole xml file?

A DOM parser (such as SimpleXML) can only load the entire document.

See: Can SimpleXML load only a partial of a XML?

but you can iteratethrough your 'who_is_online'.

for ($i=0;$i<20;$i++){    echo $xml->who_is_online[$i]->thumbnail_image;    echo $xml->who_is_online[$i]->display_name;    echo $xml->who_is_online[$i]->display_age;}