Recommended ORM for PHP

Hi list, When creating a LAMP app, I always start by writing ORM myself. It's fun but it usually takes a long time. Besides, that always results in a toy-system, I mean, that has not so many features, not so efficient non-bug-free. I started to think that now is the time to throw away my rubbish and use more effective Open source ORM. So my question is what ORM are you using? What ORM do you recommend? There're lots of Web app frameworks out there but I could't find simple ORM in PHP. Thanks in advance.