Fatal error: Uncaught SoapFault exception: [HTTP] error取回HTT

我正在尝试使用XML输出"Hello World"，但我在php页面中得到以下异常:

Fatal error: Uncaught SoapFault exception: [HTTP] error getting HTTP headers in C:'wamp'www'Web_Service'SampleXML'index.php:4 Stack trace:
#0[内部函数]:SoapClient->_doRequest('#1[内部函数]:SoapClient->_call('getHelloWorld'， Array)
#2 C:'wamp'www'Web_Service'SampleXML'index.php(4): SoapClient->getHelloWorld()
#3 {main}抛出C:'wamp'www'Web_Service'SampleXML'index.php on line 4

index . php

<?php
    $client = new SoapClient('service.wsdl');
    $response = $client->getHelloWorld(); 
    echo $response;
?>

service.wsld

<?xml version = '1.0' encoding = 'UTF-8' ?>
<definitions name = "Web Service"
    targetNamespace = 'http://example.org/service'
    xmlns:tns = 'http://example.org/service'
    xmlns:soap = 'http://schemas.xmlsoap.org/wsdl/soap/'
    xmlns:xsd = 'http://www.w3.org/2001/XMLSchema'
    xmlns:soapenc = 'http://schemas.xmlsoap.org/soap/encoding/'
    xmlns:wsdl = 'http://schemas.xmlsoap.org/wsdl/'
    xmlns = 'http://schemas.xmlsoap.org/wsdl/' >
    <!-- Message -->
    <message name='getHelloWorld'>
        <part name='response' type='xsd:string' />
    </message>
    <!-- Operations offered -->
    <portType name = 'PortType'>
        <operation name = 'getHelloWorld'>
                <!-- Target Name Space -->
                <output message = 'tns:getHelloWorld' />
        </operation>
    </portType>
    <!-- Binding Element -->
    <binding name = 'Binding' type = 'tns:PortType'>
        <soap:binding style='rpc' transport='http://schemas.xmlsoap.org/soap/http' />
        <operation name='getHelloWorld'>
            <soap:operation soapAction = 'urn:localhost-service#getHelloWorld' />
        <!-- Output -->
        <output>
            <soap:body use='encoded' namespace='urn:locahost-service' encodingStyle='http://schemas.xmlsoap.org/soap/encoding/' />
        </output>
        </operation>
    </binding>
    <!-- Define the service -->
    <service name='Service'>
        <port name='Port' binding='Binding' >
            <!-- Location -->
            <soap:address location='http://localhost/Web_Service/SampleXML/soap-server.php' />
        </port>
    </service>
</definitions>

soap-server.php

<?php
    function getHelloWorld() {
        return "Hello World";
    }
    ini_set("soap.wsdl_cache_enabled", "0");
    $server = new SoapServer('service.wsdl');
    $server->addFunction("getHelloWorld");    
    $server->handle();
?>

我在代码中错过了什么吗?