The info you need:
- PHP 5.2 was never supported by Phalcon.
- Phalcon 1.3.x is compatible with PHP 5.3.9 or higher.
- Phalcon 2.0.x is compatible with PHP 5.3.21 or higher. However it's recommended run it at least in 5.4.22.
- Phalcon 2.1.x will be only PHP >= 5.4.22 compatible.
- Phalcon should work fine with any MySQL >= 4.1.x