count xml elements/nodes using SimpleXML

this could be duplicate, but I found nothing useful so far.

I'm trying to count nodes/childs of XML file using simplexml.

I've tried this.

$xml = simplexml_load_file("./file.xml");
echo count($xml->rss->channel->item);

and

echo count($xml->item);

but just outputting 0.

here is snapshot of XML

<?xml version="1.0"?>
<rss xmlns:xsd="http://ift.tt/tphNwY"     xmlns:xsi="http://ift.tt/ra1lAU"    xmlns:g="http://ift.tt/15FVsV8" version="2.0">
  <channel>
    <item>
      <title>PUDRA Pudra Ceket Ceket</title>
      <link>http://ift.tt/1zGULXt;
       <description>36 pudra pudra ceket ıw6140005046 ipekyol ceket kadın</description>
       <g:urunid>1423905</g:urunid>
       <g:id>1423905_14</g:id>
    </item>
    <item>
        ....
    </item>