There are too many unimpressive ORM projects. There's a hundred PHP frameworks and half of them decide to roll their own ORM rather than use and contribute to an existing project.

So you're left with a lot of unsophisticated systems.

Doctrine (PHP), DataMapper (Ruby), SqlAlchemy (Python), LiNQ (.Net), Hibernate (Java). I've used all of these a great deal (except Hibernate, I've not done all that much Java).

All of these projects are sophisticated, complex, impressive. Propel? CakePHP ORM? Or just search php orm -doctrine -propel and look at the 3 dozen results.

These are junk. I'll stand by that assertion. Not because they're PHP, but because they were started often as a part of a larger framework without any respect paid to the fact that an ORM is a very very hard problem to solve.

Propel is completely different as of 1.6. It doesn't really use the "Criteria" objects any more. (which is probably what they're referring to)

It's much simpler now:

articles = ArticleQuery->where(column = ?, val)->groupBy(column)->limit(10)->find()

I like it, but it's still very resource-heavy.