How does one determine if a certain PHP project has evolved to the point that it's a framework?
A web application framework is a software framework that is designed to support the development of dynamic websites, Web applications and Web services. The framework aims to alleviate the overhead associated with common activities performed in Web development. For example, many frameworks provide libraries for database access, templating frameworks and session management, and they often promote code reuse.
Source: http://en.wikipedia.org/wiki/Web_application_framework
How does one determine if a certain PHP project has evolved to the point that it's a framework?
If the project has evolved into above definition, it is a framework but mostly frameworks are made on their own.
To put it simply, a framework is an skeleton on which projects are made.
By their own sense. Framework is not "something big and thrilling".
But just a toolbox.
As soon as it's possible to develop two different projects using it as a common base.
Strictly speaking, a single class you use in several projects is already a (small) framework.