Description:
------------
When a SoapServer sends back a SoapFault response with an empty faultstring, PHP will not set the $faultstring property of the thrown SoapFault object.

The following SOAP response will result in the $faultstring property not being set:
<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"><SOAP-ENV:Body><SOAP-ENV:Fault><faultcode>test</faultcode><faultstring></faultstring></SOAP-ENV:Fault></SOAP-ENV:Body></SOAP-ENV:Envelope>

Test script:
---------------
server.php: 
<?php
$server = new SoapServer(null, array('uri' => "http://test-uri/"));
function test($inputString) {
    global $server;
    $server->fault('test', '');
}
$server->addFunction("test");
$server->handle();
?>

client.php:
<?php
$client = new SoapClient(null, array('location' => "http://localhost/server.php",'uri'=> "http://test-uri/"));
try{
 echo $client->test('hello?');
}
catch(SoapFault $f) {
   echo isset($f->faultstring) ? "has faultstring\n" : "no faultstring\n";
}
?>

Expected result:
----------------
has faultstring


Actual result:
--------------
no faultstring