foreach shows attributes of first xml node only

I am trying to display attributes foreach global_ivr_variable:

$xml = '
  <response method="switchvox.ivr.globalVariables.getList">
      <result>
           <global_ivr_variables>
               <global_ivr_variable id="1" name="cid_name" value="Smith" />
               <global_ivr_variable id="2" name="Q_ID_Global" value="COS" />
           </global_ivr_variables>
      </result>
  </response>
';

$sxml = simplexml_load_string($xml);

foreach($sxml->result->global_ivr_variables->global_ivr_variable->attributes() as $a => $b)
{
echo $a .'=' . $b . "<br>";
}

All I get is the attributes of the first node:

id="1"
name="cid_name"
value="Smith"

I've also tried the following, which gives me no values at all...

    foreach($sxml->result->global_ivr_variables as $xvar)
    {
     $a = $xvar->global_ivr_variable->id;
     $b = $xvar->global_ivr_variable->name;
     $c = $xvar->global_ivr_variable->value;
     echo 'a='.$a.', b='.$b.', c='.$c.'<br>';
    }

a=, b=, c=

Thank you all who step up to help the needy!