Description:
------------
The PHP-Version is 5.3.3-7 (was not able to select this version in the dropdown box)

When storing a SimpleXMLObject to a class property the property is null sometimes (every 3rd - 5th call).

According to this error, PHP seems to loose all object descriptors ($this) in *all* classes, which leads to misleading error messages like "trying to get property of non-object in ..", even if I checked $this to be an object 1 line before the error message happens (How can $this be not an object? I am always in object context). 


Current solution: When casting the SimpleXMLObject to an Array and storing it to the class property both problems do not appear.

Test script:
---------------
class ProjectXML {

  private $project_xml;

  public function foo((SimpleXMLObject) $xml, $search_criteria) {
    // search a specific node, save it to the class property and return true
    $this->project_xml = $xml_node;
    return true;
  }

  public function bar() {
    var_dump($this->project_xml);
  }

}

$class = new ProjectXML();
$class->foo(simplexml_load_file("/path/to/project.xml"));
$class->bar();

/*
The used code is very complex, so I reduced it to a minimum. The full code can be viewed here: 
http://quantum-framework.org/ProjectXML.class.phps
*/

Expected result:
----------------
SimpleXMLObject

Actual result:
--------------
sometimes null
sometimes the SimpleXMLObject