How to escape colon when reading XML in PHP, simplexml

I have an XML file that I am trying to get variables off with PHP. The XML file looks like this:

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dcq="http://purl.org/dc/terms/" xmlns="http://www.skype.com/go/skypeweb">
<Status rdf:about="urn:skype:skype.com:skypeweb/1.1">

You can view the full XML file here: http://mystatus.skype.com/username.xml

I used the simplexml extension to convert the xml input into the PHP object $xml. When I attempt to navigate later in the file with:

$variable = $xml->rdf:RDF->Status->presence;

It gives me an error because of the colon in "rdf:RDF":

Parse error: syntax error, unexpected ':'

How can I either escape the colon, or navigate later in the file without changing the XML file?

Solution

Your initial code:

$variable = $xml->rdf:RDF->Status->presence;

does not work because it is creating a syntax error:

Parse error: syntax error, unexpected ':' in /test.php on line 8

The colon in the property name is not valid. PHP's common way to work with that are curly braces:

$xml->{'rdf:RDF'}->Status->presence

As you then found out you get the undefined property notice:

Notice: Trying to get property of non-object in /test.php on line 8

That is first-hand because such a property does not exists, var_dump shows that:

var_dump($xml);

class SimpleXMLElement#1 (1) {
  public $Status =>
  class SimpleXMLElement#2 (2) {
    public $statusCode =>
    string(1) "1"
    public $presence =>
    array(13) {
      [0] =>
      string(1) "1"
      ...
    }
  }
}

However, apart from that, even if there would be a children with a namespace prefixed element name, it would not work that way. This would just never work, so always such a property is not defined.

However what the previous dump outlines is that there is the property you're looking for: $Status:

$variable = $xml->Status->presence;

So you were just looking in the wrong place. The var_dump($variable) is:

class SimpleXMLElement#4 (13) {
    string(1) "1"
    string(7) "Offline"
    string(12) "Déconnecté"
    string(7) "Offline"
    string(15) "オフライン"
    string(6) "離線"
    string(6) "脱机"
    string(7) "Offline"
    string(7) "Offline"
    string(12) "Non in linea"
    string(12) "Desconectado"
    string(15) "Niepodłączony"
    string(7) "Offline"
}