如何将SimpleXMLObject转换为PHP数组？

Consider the following code:

请考虑以下代码：

$string = '<device>
    <id>1234</id>
    <label>118</label>
    <username>root</username>
    <password>helloWorld</password>
    <hardware>
        <memory>4GB RAM</memory>
        <storage_drives>
            <storage_drive_1>2TB SATA 7,200RPM</storage_drive_1>
            <storage_drive_2>1TB SATA 7,200RPM</storage_drive_2>
            <storage_drive_3>Not Applicable</storage_drive_3>
            <storage_drive_4>Not Applicable</storage_drive_4>
        </storage_drives>
    </hardware>
</device>';
$xml = new SimpleXMLElement($string);

$deviceDetails = Array();
foreach($xml as $element){
    $tag = $element->getName();
    $deviceDetails +=  Array($tag => '$element->$tag)',
        );
    }
$stri