Ask HN: which (web)framework should I focus on?

I'm currently work on a few new projects that are in a early, me being the only coder (with some friends occasionally contributing), stage. These projects are all web focused (with iPhone/Android apps in the feature pipeline) and I'm having a hard time deciding on what framework I should commit to.

The current code-base is a straight forward ajax->php->mysql system. I'm trying to decide wether I should switch to a ruby-mongoDB, python-mongoDB, java/scala-mongoDB, node-mongoDB or couchApp/CouchDB or stick with php.

The data I'm using right now is well suited for a document based database so that isn't a problem (at least at the moment), I know all the languages but scala well enough for this.

What I'm wondering about is how resource demanding the non-apache servers are and basically if stability will be a problem with them? If anybody has any experiences with managing a project in those frameworks?

Also which framework you would recommend learning for the future (which one you'd like to know/hire someone who knows)?