gistfile1.php

<?php

class DoctrineProductRepository implements ProductRepository {

	//entity manager
	protected $em;

	public function addCategory(ProductInterface $product, CategoryInterface $category)
	{
		$product->setCategory($category);

		$this->em->persist($category);
		$this->em->persist($product);
	}

	public function flush()
	{
		$this->em->flush();
	}
}

class PropelProductRepository implements ProductRepository {

	protected $toSave = [];

	public function addCategory(ProductInterface $product, CategoryInterface $category)
	{
		$product->setCategory($category);

		$this->soSave[] = $product;
	}

	public function flush()
	{
		if ! empty($this->toSave) {

			$con = Propel::getConnection(MyApp::DATABASE_NAME);

			$con->beginTransaction();

			try {
				
				foreach ($this->toSave as $model) {

					$model->save();
				}

				$con->commit();

				$this->toSave = [];

			} catch (Exception $e) {

				$con->rollback();
				throw $e;
			}
		}
	}
}

class EloquentProductRepository implements ProductRepository {

	protected $toSave = [];

	public function addCategory(ProductInterface $product, CategoryInterface $category)
	{
		$this->toSave[] = function() use ($product, $catgory) {
		
			$product->category()->save($category);
		}
	}

	public function flush()
	{
		if( ! empty($this->toSave)) {

			DB::transaction(function()
			{
			    foreach ($this->toSave as $closure) {

			    	$closure();
			    }

			    $this->toSave = [];
			});
		}
	}
}