Simpliform is a form processing library for PHP with very configurable processing behaviour without having many APIs to learn:
$form = new Simpliform(); $form->addFilter('field', function($context) { return $context->getValue() * 10; }); $form->setInput(array( 'field' => "10", )); $processed = $form->getOutput(); var_dump($processed); // array('field' => 20);
Currently a work in progress with many unfinished features. Unless you want to steal bits of it or make patches it's probably best to avoid for now.