You can do this with "classmap" option in SoapClient/SoapServer constructor.

$client = new SoapClient(("http://localhost:8080/axis/base?wsdl",
  array("classmap"=>array("SOAPStruct"=>"SOAPStruct")));

Thanks Dimitri for this pointer. It actually seem to work  
for the example I posted.  
  
Nevertheless, when using an array of wsdl-structs, the  
classmap specifiaction seems to be ignored: 
 
To be precise, when I extend my example with the following 
code: 
----------------------- 
echo "********* echoStruct:\n"; 
echo "**** s:\n"; $s->printMe(); 
$r = $client->echoStruct($s); 
echo "**** r:\n"; $r->printMe(); 
$sa = array(new SOAPStruct("s_string0",43,3.1415926535), 
            new SOAPStruct("s_string1",44,17.47), 
            new SOAPStruct("s_string2",45,27.30)); 
 
$ra = $client->echoStructArray($sa); 
 
echo "**** sa:\n"; 
     foreach($sa as $key => $value) { 
       echo "$key => "; $value->printMe();  
     } 
echo "**** ra:\n"; 
     foreach($ra as $key => $value) { 
       echo "$key => "; $value->printMe(); <--- 
     } 
----------------- 
, I get the following error: 
Fatal error: Call to undefined method stdClass::printMe() 
in /home/wglas/axis/php/base.php on line 68 
The line number refers to the line marked with <--- above. 
The code for returning a single structure (echoStruct call 
above) is running without any problem. 
 
So it seems to me, that members of an array of wsdl-structs 
are mapped to stdclass, regardless of the classmap 
directive in the SOAPClient ctor. 
 
   Wolfgang

I just tested this with PHP-5.0.3 and latest CVS versions. Works fine for me.

<?php
class SoapStruct {
  public    $varString;
  protected $varInt;
  private   $varFloat;

  function SoapStruct($a, $b, $c) {
    $this->varString = $a;
    $this->varInt = $b;
    $this->varFloat = $c;
  }

  function printMe() {
    var_dump($this);
  }
}

function echoStructArray($a) {
  return $a;
}

class LocalSoapClient extends SoapClient {
  function __construct($wsdl, $options) {
    parent::__construct($wsdl, $options);
    $this->server = new SoapServer($wsdl, $options);
    $this->server->addFunction('echoStructArray');
  }

  function __doRequest($request, $location, $action, $version) {
    ob_start();
    $this->server->handle($request);
    $response = ob_get_contents();
    ob_end_clean();
    return $response;
  }

}

$x = new LocalSoapClient("round2_base.wsdl", 
                         array("classmap"=>array("SOAPStruct"=>"SOAPStruct")));
$y = $x->echoStructArray(array(new SoapStruct("0", 3, 4.1),
                               new SoapStruct("1", 5, 6.2)));
foreach($y as $z) {
  $z->printMe();
}
?>