How-to parse XML key:value pair

I have a clients server returning the following (strange) XML response; how do I access each key:value pair?

$xml = '<?xml version="1.0"?>
  <response>
    <string key="__status">success</string>
    <string key="id">1000</string>
    <string key="m开发者_如何学运维ask">9999</string>
</response>';

I was hoping that the following would work, but it appears not.

$test = new SimpleXMLElement($xml);
echo "Mask: " . $xml->response->mask; // Mask: 9999

---

If you want a specific element, you can use XPath:

$matches = $test->xpath('//string[@key="mask"]');

(this requires PHP 5.2)

This would give you:

Array
(
    [0] => SimpleXMLElement Object
        (
            [@attributes] => Array
                (
                    [key] => mask
                )

            [0] => 9999
        )
)   

If you want all elements, you have to iterate over all string elements and access their text and key attribute:

$items = array();

foreach($test->string as $item) {
    $items[(string) $item->attributes()->key] = (string) $item;
}

gives:

Array
(
    [__status] => success
    [id] => 1000
    [mask] => 9999
) 

---

<pre>
<?php
$xml = '<?xml version="1.0"?>
  <response>
    <string key="__status">success</string>
    <string key="id">1000</string>
    <string key="mask">9999</string>
</response>';

$test = new SimpleXMLElement($xml);
echo "Mask = ".$test->string[2];
?>
</pre>

Here is the working code.

---

if my memory server me right simplexml is extension. Are you sure you installed it? BTW, simplexml was added in PHP 5.0, so make sure you are not running lower version