Ask HN: Which is the best php framework in terms of performance?

I have been thinking about writing a web MVC based application in PHP (though i dont have prior php programming experience)

Initially i settled with Zend framework, and was satisfied with the tutorials available; the rich feature set it presented; but lately googled and found that the number of requests that it can handle is very meagre.

Since I did not hear about any enterprise applications built in the Zend framework I decided to switch to DooPhp.

After researching a bit abt the various available frameworks (Zend Framework, Code Igniter, Yii, DooPhp, Prado, Kohana, SolarPHP .... ) I found that there isnt much genuine comparisons done!

We are building an application which will connect to a database(Postgres) and would do basic CRUD operations, require features for sending html mails, pdf creation and reporting tools(to represent data graphically).

We dont expect very heavy loads; but in case we would definitely want to scale.

Which is the best php framework I should choose?