Formal\Form\Morphology::keyForPropName PHP Method

    protected function keyForPropName($sPropName)
    {
        $aKeys = $this->oElements->keys();
        reset($aKeys);
        foreach ($aKeys as $sKey) {
            $oElement = $this->oElements->getForKey($sKey);
            if ($oElement->option("prop") === $sPropName) {
                return $sKey;
            }
        }
        return false;
    }