s_i_l_e_n_c_e_r

abstract class AbsctactFileProcessor
{
    abstract public function supports($extension);
    abstract public function process($file);
}

class ProcessingProvider
{
    
    private $processors;

    public function __construct()
    {
        $this->processors = array();
    }

    public function addProcessor(AbsctactFileProcessor $processor)
    {
        $this->processors[] = $processor;

        return $this;
    }

    public function process($file)
    {
        $file = new \SplFileInfo($file);
        $extension = $file->getExtension();
        foreach ($this->processors as $processor) {
            if ($processor->supports($extension)) {

                return $processor->process($file);
            }
        }

        throw new \LogicException();
    }

}

class SimpleTextProcessor extends AbsctactFileProcessor
{

    public function process($file)
    {
        // return ...
    }

    public function supports($extension)
    {
        return in_array($extension, array('txt'));
    }

}

class ImageProcessor extends AbsctactFileProcessor
{

    public function process($file)
    {
        // return ...
    }

    public function supports($extension)
    {
        return in_array($extension, array('png', 'gif', 'bmp', 'jpg'));
    }
}

$provider = new ProcessingProvider();
$provider->addProcessor(new \SimpleTextProcessor());
$provider->addProcessor(new \ImageProcessor());

$provider->process('mybestfile.exe');