PHP：XML解析错误 - simplexml_load_string（）期望参数1为字符串

Question

我正在尝试解析PHP中方法的XML响应.Below是我的回复。

响应：

<FindIssuesResponse xmlns="http://Service/">
    <FindIssuesResult>
    <FindIssues xmlns="">
    <GetIssue>
    </GetIssue>
    <GetIssue>
      <IssuesIssueNbr>1226</IssuesIssueNbr>
      <IssuesIssueDescription>Issue Descreption</IssuesIssueDescription> 
      <IssuesIssueSolution>Duplicate ticket for Issue #1223</IssuesIssueSolution> 
      <IssuesIssueTypeID>7</IssuesIssueTypeID> 
      <IssueNotes>
        <NotesIssueNbr>1226</NotesIssueNbr> 
        <NotesNoteID>16344</NotesNoteID> 
        <NotesNoteCreatedDate>2013-10-23T01:28:50.383-04:00</NotesNoteCreatedDate> 
        <NotesNoteText>text</NotesNoteText>
        <NotesNotePrivate>false</NotesNotePrivate> 
        <NotesFirstNote>true</NotesFirstNote> 
        <NotesDatabaseID>IssueTrak</NotesDatabaseID> 
        <NotesCreatedBy>user@example.com</NotesCreatedBy> 
        <NotesNoteTime>0</NotesNoteTime> 
        <NotesIsRichText>true</NotesIsRichText> 
      </IssueNotes>
     </GetIssue>
    <GetIssue>
    </GetIssue>
    <GetIssue>
    </GetIssue>

请帮我解析这个XML以获取第一个标记值“NotesIssueNbr”

我写的是这样的。

代码：

<?php
require_once 'nusoap.php';
$wsdl="D:\PHP\ITAlert.wsdl";
$client=new SoapClient($wsdl);
$searchCriteria='<FindIssues><ReturnSchema>N</ReturnSchema><IssueStatus>Open</IssueStatus><IssuesNextActionBy><UsersUserID>user@example.com</UsersUserID></IssuesNextActionBy></FindIssues>';
$params=array('searchCriteria'=>$searchCriteria,'username'=>'user@example.com','password'=>'password');  

$response = $client->__soapCall('FindIssues', array($params));

$issues = simplexml_load_string($response->FindIssuesResult);

$value1=$issues->issues->FindIssues->GetIssue->IssuesIssueNbr;
echo $value1;
?>

我是否知道解析此格式的方法

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
   <soap:Body>
      <FindIssuesResponse xmlns="http://IssueTrakService/">
         <FindIssuesResult>
            <FindIssues xmlns="">
               <GetIssue>
                  <IssuesIssueNbr>1223</IssuesIssueNbr>