Not for 'how-to' coding questions but PHP theory instead, this forum is here for those of us who wish to learn about design aspects of programming with PHP.
It's an example of lazy loading: rather than defining different validation methods in one class, you'd extend a common Validator base class with nice 'n slim classes which perform different types of tests.
The performance gains would admittedly be more theoretical rather than real. Possibly the extra HD seeks would even count against Strategy, depending on just how many validation methods you have defined in the all-in-one class. We're into Hubble telescope territory though: there wouldn't be any noticable difference either way, I think.
Strategy just feels better - leaner and meaner like good OOP classes should be.
Oh Ghost, I forgot to mention something I heard somewhere (forget where)
The way you inherit from your config file doesn't meet the requirements of inheritence.
You should only inherit from something if there is an "is a" relationship. For example, a customer "is a" person and an employee "is a" employee, so they could both inherit from a person object, but a config file doesnt meet that requirments for a framework.
So I think it's best to have a config object as an attribute of other classes, rather than inheriting from it. It makes sense to me, so I thought I'd mention it incase you were interested.