SimpleXML load String将值放入PHP中的Array（）中

Question

I have a XML in form of String (after XLS transform):

<course>
    <topic>
        <chapter>Some value</chapter>
        <title>Some value</title>
        <content>Some value</content>
    </topic>
    <topic>
        <chapter>Some value</chapter>
        <title>Some value</title>
        <content>Some value</content>
    </topic>
    ....
</course>

Then I'm pushing above mentioned XML into the Array():

$new_xml = $proc->transformToXML($xml);

$xml2 = simplexml_load_string($new_xml);
$root = $xml2->xpath("//topic");

$current = 0;
$topics_list = array();

// put the xml values into multidimensional array
foreach($root as $data) {
    if ($data === 'chapter') {
        $topics_list[$current]['chapter'] = $data->chapter;
    }
    if ($data === 'title') {
        $topics_list[$current]['title'] = $data->title;
    }
    if ($data === 'content') {
        $topics_list[$current]['content'] = $data->content;
    }
    $current++;
}
print_r($topics_list);

Problem: Result is empty array. I've tried string like:

$topics_list[$current]['chapter'] = (string) $data->chapter;

but result is still empty. Can anyone explain, where is my mistake. Thanks.

Answer 1

Because my topic element has only simple child elements and not attributes, I can cast it to array and add it to the list (Demo):

$xml2 = SimpleXMLElement($new_xml);
$topics_list = array();
foreach ($xml2->children() as $data) {
    $topics_list[] = (array) $data;
}

The alternative method is to map get_object_vars on the topic elements (Demo):

$topics_list = array_map('get_object_vars', iterator_to_array($xml2->topic, false));

But that might become a bit hard to read/follow. Foreach is probably more appropriate.

---

And here is the first working version of my code:

$xml2 = SimpleXMLElement($new_xml);
$current = 0;
$topics_list = array();
foreach($xml2->children() as $data) {
    $topics_list[$current]['chapter'] = (string) $data->chapter;
    $topics_list[$current]['title'] = (string) $data->title;
    $topics_list[$current]['content'] = (string) $data->content;
    $current++;
}

Thanks again to @Jack, @CoursesWeb and @fab for their investigation.