Which PHP frameworks are used by corporations?

There are several questions about PHP frameworks, but I’m curious as to which one(s) are used in the commercial world when developing web applications with PHP. At my first web-based job, they didn’t have a framework for the PHP codebase. Is this common when dealing with PHP? If not, what frameworks to companies producing a product (either a site that provides a service of some kind or a web-based product that can be purchased) using PHP tend to use?

Which PHP frameworks are used by corporations?