In my opinion the best ORM for PHP is Doctrine.
You may also wish to check out Propel and see which suits your style better.
PHP ORMs: Doctrine vs. Propel is a recent SO question comparing the two. Common PHP frameworks like Symfony let you use either ORM as far as I recall.
As far as POJOs, as far as I know you'd use stdClass for that in PHP. I'm not much with Java though, so I can't say for sure. Here's an SO Question about that... What is stdClass in PHP?