How can I read the XML in php? [closed]

I cannot read the XML in php. I am getting a response in XML and I need to show it in a ul/li tag in php. Its like a order tracking API which is giving a response in XML format.

<?php 
$xml='<?xml version="1.0" encoding="utf-8"?>
<vendor-objects version="1.0">
    <object vk="1"
            model="vb">
        <field type="BigIntegerField"
               name="dono">12345</field>
        <field type="CharField"
               name="pid">DHI89</field>
        <field type="FloatField"
               name="dwei">1</field>
        <field name="xcvi">
            <object vk="1"
                    model="v_stage">
                <field type="CharField"
                       name="serty">Item no</field>
            </object>
            <object vk="2"
                    model="v_stage">
                <field type="CharField"
                       name="serty">P no</field>
            </object>
        </field>
    </object>
</vendor-objects>
';


$devices = array();
$xml = simplexml_load_string($xml);
foreach($xml->field->object as $item)
{
   $device = array();

   foreach($item as $key => $value)
   {
        $device[(string)$key] = (string)$value;
   }

   $devices[] = $device;
}
print_r($devices);
?>