gistfile1.php

<?php

interface Configurable
{
    static function getOptionsBag();
}

class Form implements Configurable
{
    public function __construct($options = array())
    {
        $this->options = static::getOptionsBag()->process($options);
    }

    static public function getOptionsBag()
    {
        return OptionsBag::create()
            ->addRequiredOption('foo')
            ->addOption('bar', 'blah')
        ;
    }
}

This does not allow for instance variables of the options but keeps the stupid $options array that has no meaning :)

Well, that could be done in the constructor, if that's what you want. We could also add some simple "binding" logic to the options bag that sets properties on the configurable object. I don't see the problem with an options array, myself.

The code is so unexplicit, when your field wiggles with 20 or something options is really bad to read getOption('a') getOption('b)' only ... and so on.

Why the static bag btw? Is there any metadata need for this? I can't really see it yet.