XML : How to read elements like

I have an api service which returns xml of the below kind:

  <KidsAges xmlns:a="http://schemas.microsoft.com/2003/10/Serialization/Arrays">      <a:int>3</a:int>      <a:int>4</a:int>  </KidsAges>    

Now here the element denotes that there were 2 kids in the room. How can I read this while using simplexml with PHP. I just want to count the number of elements .

Thanks.