What do you think about the subject?

Metaprogramming is most commonly associated with non-dynamic languages, since there's an harder time in achieving certain behaviours (such as implementing an ORM) without lots of non-productive and non-intelligent lines of code.

But even in more dynamic languages such as PHP, code generation can be a really life-saver and increase productivity in massive amount. In modern frameworks it's very common to have scaffolding that generates most of the common model, form, test and actions for a certain business object that you declare. It's one of the reasons why frameworks such as symfony or RoR have so much success, those code-generation tools make consistent code very quickly and boost the programmers productivity.

In web-sites, most of the interaction revolves around four main actions:

• Create an element
• Retrieve a set of elements (with possible filtering)
• Update an element with new attributes
• Delete a set of elements

At least everything that revolves around this 4 main actions could and IMHO SHOULD be achieved using code-generation tools to achieve maximum-productivity.

In my company, we use symfony, and its admin-generator is an exceptional tool, that even generates code in run-time (and caches it), which means we don't even need to use any kind of task or external tool to generate new code, we just need to clean our cache. I STRONGLY advise into using this kind of tool for CRUD operations.

But, doing what symfony awesome contributors did, is not an easy task. I've implemented some code-generation tasks myself and doing something that is truly consistent and with a broad implementation to cover most corner-cases is not easy.

Is it something that will really increase your productivity?

I believe that metaprogramming is very very important in lower-levels of work (frameworks, caching, compilers, etc.) but something that we must approach with extreme caution if we're doing things on the business-layer.

Using code-generation is without any question a major productivity-booster. Implementing your own code-generation tools, not so much unless you're building a framework yourself.

What are some good resources on the subject, among books, blogs, slideshows, etc?

The best resource to understand programming is always good and well-commented source code. I would say that looking into RubyOnRails and Symfony admin generators is a good idea.