I guess many peoples calls getLastRequest and it returns nothing. "Heey where is the my last request". Now we will see our request,  when you created a SoapClient instance, you should give a option parameter as below :

<?php
// below $option=array('trace',1);
// correct one is below
$option=array('trace'=>1);

$client=new SoapClient('some.wsdl',$option);

try{
  $client->aMethodAtRemote();
}catch(SoapFault $fault){
  // <xmp> tag displays xml output in html
  echo 'Request : <br/><xmp>',
  $client->__getLastRequest(),
  '</xmp><br/><br/> Error Message : <br/>',
  $fault->getMessage();
}
?>

"trace" parameter enables output of request. Now, you should see SOAP request.