It came out almost 2 years ago, but it to me that many programmers around me have no idea about it. Myself, I have learned about it around 6 months ago. The PHP documentation defines late static binding as a way to "reference the called class in a context of static inheritance." This definition didn't really help me the first time I read it. Fortunately, there are more explanations in the documentation, and there are good examples. If you haven't, you should read it.

To clarify, he includes a code snippet showing the use of the "static" keyword to correctly reference a static method. He also includes in interesting bit about when's a good time to use it.

First, he talks about the Factory pattern:

At some point in developing, developers will discover a need to support switching among various methods of performing an action. The example I used in a forum post earlier was Database Abstraction. Say for a moment you want to separate all the logic needed to create an Abstraction object (say using ADOdb Lite) into a central place for easier control. At this point the Factory Pattern starts rearing its head.

Of course, a bit of sample code is given to illustrate the point, creating the instance of an ADOdb object.

Next up is the Abstract Factory pattern - the difference being that these make it easy to switch between Factories using different resource (such as his example to switch between ADODB and PDO).

In these cases, we will have multiple Factories. However instead of one generically named Factory, we will have several specific Factories. This should (eventually) lead us to impose a parent class, which will allow duplicated code from each specific DatabaseAbstractionFactory to be moved up to the common parent class.

Just as before, they provide example code to illustrate the use of this slightly different pattern.