Using a class to handle the output of another class

Hello everybody!

I'm having a little problem with the following: I wrote a class to
collect data (Let's call it DataCollector). Now I want the data to be
interpreted in various ways. My idea was to write an interface
(iVisualizer) so DataCollector could use every user defined
(MyVisualizer) class implementing it. Saying "MyVisualizer extends
DataCollector" is not an option, since the data should only be
collected once and then then being "rendered" by a variety of output
classes (to XML, to plain text, to PDF, etc.).

Here is the code example:


class DataCollector {
private $data

public function collectData ($someText) {
// Write data here
}

public function output($visualizer) {
$visualizer->output($this)
}
}

class MyVisualizer implements iVisualizer {
public function output ($dataCollector)
{
echo $dataCollector->data;
}
}

$a = new DataCollector();
$b = new MyVisualizer();
$a->collectData("foo");
$a->output($b);


Now, obviously calling "$a->output($b);" will get me in trouble, since
DataCollector::data is private. Making DataCollector::data public
would make it easy, but also "unsafe". Adding get & set methods will
add lots of methods, since $data is just an example for a large number
of properties.

I really hope to get some good ideas here. Thanks in advance!

Oli