The ServerGrove blog has posted their latest in-depth look at one of the many components that make up the Symfony2 framework. In this latest post they cover the Validator component, another well-used part of the framework.

In the first five posts of this series we have been talking about key components for any PHP framework from the point of view of their internals, such as HttpFoundation to abstract the HTTP protocol, HttpKernel to convert a Request into a Response, Routing to map requests to controllers, EventDispatcher to add reusability and extensibility, and Config to load and validate configuration values. This time we'll delve deeper in the user space to describe a component that is for specific apps rather than just for frameworks. Today's topic will be the Validator component.

They start off talking about a common problem in web applications, running validation on incoming data, and how the component can help. The article then gets into the architecture of the component and provides a simple example of it in use (validating an integer range). They talk about some of the built-in validations, the internationalization support and validation on objects, just just simple values. Finally, there's a look at creating custom validations, their example being a simple check on a given "programming language" string.