In this new post Ralph Schindler takes a look at the Prototype design pattern and uses it to illustrate some best practices in using constructors in PHP.
If your knowledge of constructors ends with "the place where I put my object initialization code," read on. While this is mostly what a constructor is, the way a developer crafts their class constructor greatly impacts the initial API of a particular class/object; which ultimately affects usability and extensibility. After all, the constructor is the first impression a particular class can make.
He starts at ground level, reintroducing what a constructor is and what it should (and shouldn't) be used for. He talks about constructor overloading, constructor injection, dynamic class extension and using the Prototype pattern to create "an unlimited number of objects of a particular type, with dependencies in tact, each with slight variations." He gives an example with a "DbAdapter" class, showing dynamic class instantiation and how to, using the Prototype method, inject a DbAdapter object and have your class use that instead.