Constructors as factory methods

Is there any concensus on can a class constructor act as a factory method? For example if I have a classes Car Car_Lada and Car_Porche, I would like to make the constructor return the concrete class like: $c = new Car("Lada") instead of using c= new Car::Factory("Lada") However looking at other PEAR classes they all use a static factory method call to return the concrete object. Which way is preferred? -- Mika Tuupola http://www.appelsiini.net/~tuupola/