public function addForeignKey($foreignKey)
    {
        if ($foreignKey instanceof ForeignKey) {
            $fk = $foreignKey;
            $fk->setTable($this);

            $name = $fk->getPhpName() ?: $fk->getName();
            if (isset($this->foreignKeysByName[$name])) {
                throw new EngineException(sprintf('Foreign key "%s" declared twice in table "%s". Please specify a different php name!', $name, $this->getName()));
            }

            $this->foreignKeys[] = $fk;
            $this->foreignKeysByName[$name] = $fk;

            if (!in_array($fk->getForeignTableName(), $this->foreignTableNames)) {
                $this->foreignTableNames[] = $fk->getForeignTableName();
            }

            return $fk;
        }

        $fk = new ForeignKey(isset($foreignKey['name'])? $foreignKey['name'] :null );
        $fk->setTable($this);
        $fk->loadMapping($foreignKey);

        return $this->addForeignKey($fk);
    }