使用php更新xml中的节点属性

Question

Is it possible to update the node attributes of an xml using simplexml? example:-my program is actually a quiz editor for teacher, as a teacher, i want to edit a specific question attributes. ie

<Quiz>
<topic text="Preparation for Exam">
    <subtopic text="Math">
              <question text="1 + 1 = ?"> 
              <answer num="A" Text="1" /> 
              <answer num="B" Text="2" /> 
              <answer num="C" Text="3" /> 
              <answer num="D" Text="4" /> 
              </question>
              <question text="4 * 4 = ?" > 
              <answer num="A" Text="12" /> 
              <answer num="B" Text="14" /> 
              <answer num="C" Text="16" /> 
              <answer num="D" Text="18" /> 
              </question>
       </subtopic>
       </topic>
       </Quiz>

is it possible? though i have tried a lot of ways ie by deleting the previous node and then inserting the edited one. but this trick only works for last node... for other nodes it just do swapping

Answer 1

<?php
$subtopic = new SimpleXMLELement(data());
$subtopic->question[1]['text'] = 'lalala';
$subtopic->question[1]['foo'] = 'bar';

foreach( $subtopic->question[1]->answer as $answer) {
    $answer['Text'] .= '(dez)';
}

echo $subtopic->asXML();


function data() {
    return <<< eox
<subtopic text="Math">
<question text="1 + 1 = ?"> 
<answer num="A" Text="1" /> 
<answer num="B" Text="2" /> 
<answer num="C" Text="3" /> 
<answer num="D" Text="4" /> 
</question>
<question text="4 * 4 = ?" > 
<answer num="A" Text="12" /> 
<answer num="B" Text="14" /> 
<answer num="C" Text="16" /> 
<answer num="D" Text="18" /> 
</question>
</subtopic>
eox;
}

prints

<?xml version="1.0"?>
<subtopic text="Math">
<question text="1 + 1 = ?"> 
<answer num="A" Text="1"/> 
<answer num="B" Text="2"/> 
<answer num="C" Text="3"/> 
<answer num="D" Text="4"/> 
</question>
<question text="lalala" foo="bar"> 
<answer num="A" Text="12(dez)"/> 
<answer num="B" Text="14(dez)"/> 
<answer num="C" Text="16(dez)"/> 
<answer num="D" Text="18(dez)"/> 
</question>
</subtopic>