PHP使用simplexml_load_string加载XML文档

Question

I am new to work with XML files. I've been trying to load the an XML document with the following format as object or array: After the this edit

<?xml version="1.0"?>
<xdm:Device xmlns:xdm="http://www.example.com/schemas/imaging/con/xdm/1.1/" 
           xmlns:dd="http://www.example.com/schemas/imaging/con/dictionaries/1.0/" 
           xmlns:bsi="http://www.example.com/schemas/imaging/con/bsi/2003/08/21" 
           xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" 
           xmlns:count="http://www.example.com/schemas/imaging/con/counter/2006/01/13" 
           xmlns:media="http://www.example.com/schemas/imaging/con/media/2006/01/13/" 
           xmlns:xsi="http://www.example.org/2001/XMLSchema-instance" 
           xmlns:tt="http://www.example.com/schemas/imaging/con/capabilities/1.1/" 
           xmlns:pwg="http://www.example.com/schemas/imaging/con/pwg/sm/1.0/">
    <xdm:Information>        
        <xdm:Component id="system" componentType="system">
            <dd:MakeAndModel>Samsung LaserJet ML220</dd:MakeAndModel>
            <dd:Description>Blackand while printer</dd:Description>
            <dd:ProductNumber>XB3zzz</dd:ProductNumber>
            <dd:Manufacturer>
                <dd:Name>Samsung</dd:Name>
            </dd:Manufacturer>
        </xdm:Component>
    </xdm:Information>    
</xdm:Device>

I would like to get from every entrance for instance the MakeAndModel, Description, Manufacturer, etc.

I am trying to load the code with the following code currently, but I've tried a lot of things:

$xmlString = file_get_contents('test.xml');
$xml = simplexml_load_string($xmlString); 
var_dump($xml);

I have tried with other simpler XML documents and it works fine. But with my document it does not work, it loads an empty object instead. The file does not have a title. I read in php.net the following in one of the examples:

// The file test.xml contains an XML document with a root element // and at least an element /[root]/title.

How can I achieve load this XML to array or Object?

Edit2:

When I use a simple XML file from example var_dump outputs the following:

[root@windows8 csvmail]# php ppp.php 
object(SimpleXMLElement)#1 (1) {
  ["movie"]=>
  object(SimpleXMLElement)#2 (5) {
    ["title"]=>
    string(22) "PHP: Behind the Parser"

Whit the real file if get the following:

[root@windows8 csvmail]# php ppp.php 
object(SimpleXMLElement)#1 (0) {
}
[root@windows8 csvmail]# 

Answer 1

The nodes with : in them are in "XML namespaces". They are used to mix multiple types of data into one file, even if the tag names would otherwise collide.

At the top of the file, the xmlns:... attributes associate prefixes (which could be changed by whatever is generating the file) with URLs (which act as a permanent identifier for a particular type of data).

To access them with SimpleXML, you use the ->children() method to "select" the namespace. You can rely on the prefix not changing, or you can store the permanent identifiers in a variable or constant, and use that, like this:

// Defining my own ways of referring to the namespaces, regardless of prefix used
define('XMLNS_HP_XDM_1_1', 'http://www.hp.com/schemas/imaging/con/xdm/1.1/');
define('XMLNS_HP_DICT_1_0', 'http://www.hp.com/schemas/imaging/con/dictionaries/1.0/');

// Load the XML in the normal way
$sx = simplexml_load_string($xml);

// Switch to the first namespace, and look at the first Component
$component = $sx->children(XMLNS_HP_XDM_1_1)->Information->Component;

// Attributes with no : in are technically in no namespace at all,
// so we have to switch back to the null namespace using attributes()
$component_id = (string)$component->attributes(null)->id;

// Switch to the second namespace to find the MakeAndModel
$make_and_model = (string)$component->children(XMLNS_HP_DICT_1_0)->MakeAndModel;

echo "$component_id : $make_and_model";

[Live Demo]

For how to loop over multiple elements, and other basic usage, see the examples in the PHP manual.