如何使用 PHP SoapClient 发送此 XML？

Question

I am trying to send the XML request below using PHP Soap Client, but the servers responds with the error Error fetching http headers . 我想主要问题来自如何正确解释transactionProperties下的元素entry

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ext="http://xxx.xxx.xxx.xxx.com/">
   <soapenv:Header/>
   <soapenv:Body>
        <ext:requestPurchase>
            <context>
                <channel>xxx</channel>
                <prepareOnly>xxxx</prepareOnly>
                <clientReference>12q31a1a456677881</clientReference>
                <clientRequestTimeout>500</clientRequestTimeout>
                <initiatorPrincipalId>
                <id>xxxx</id>
                <type>xxxx</type>
                <userId>xxxx</userId>
                </initiatorPrincipalId>
                <password>xxxxx</password>
                <transactionProperties>
                <entry>
                    <key>preferredLanguage</key>
                    <value>en</value>
                </entry>
                <entry>
                    <key>productSKU</key>
                    <value>xxx</value>
                </entry>
                <entry>
                    <key>currency</key>
                    <value>NGN</value>
                </entry>
                <entry>
                    <key>purchaseAmount</key>
                    <value>3</value>
                </entry>
                </transactionProperties>
            </context>
            <purchaseOrder>
                <productSpecifier>
                <productId>xx</productId>
                <productIdType>xxx</productIdType>
                </productSpecifier>
                <purchaseCount>5</purchaseCount>
            </purchaseOrder>
        </ext:requestPurchase>
   </soapenv:Body>
</soapenv:Envelope>

这是我的代码：

<?php
// Setup Host,WSDL location, Soap Client options
$uri = "http://xx.xxx.xx.x.com/";
$wsdl = "http://host-ip/xxx/service?wsdl"; 
$soapclientOptions = array();
$soapclientOptions['trace'] = TRUE;
$soapclientOptions['exceptions'] = 1;
$soapclientOptions['use'] = 'SOAP_LITERAL';
$soapclientOptions['uri'] = $uri;
$soapclientOptions['connection_timeout']  = 15;
$soapclientOptions['cache_wsdl'] = WSDL_CACHE_NONE;

$e = '';
try 
{
    $client = new SoapClient($wsdl, $soapclientOptions);
}
catch(Exception $e)  
{
    die('Error occured on attempt to open Soap Connection. Check log for error details');
}

try
{
    $payload = array(
        "context"=>array("channel"=>"xxx", "prepareOnly"=>xxx, "clientReference"=>"12q31a1a456677881",
        "clientRequestTimeout"=>"500", "initiatorPrincipalId"=>array("id"=>"xxx", "type"=>"xxx", "userId"=>"xxx"),
        "password"=>"xxxx", "transactionProperties"=>array( 
                array("key"=>"preferredLanguage", "value"=>"en"),
                array("key"=>"productSKU", "value"=>"VOS"),
                array("key"=>"currency", "value"=>"NGN"),
                array("key"=>"purchaseAmount", "value"=>"3")
                )
        ),
        "purchaseOrder"=>array("productSpecifier"=>array("productId"=>"xxx","productIdType"=>"xxx"),"purchaseCount"=>"5")
    );
    $result = $client->requestPurchase($payload);
}
catch (Exception $e)
{
    die('Error occured on attempt to process Soap Connection. Check log for error details');
}