Thought: I agree with you that passing numerous arguments to a constructor can get unwieldy, and that using a setter gives you a cleaner approach.

However, one might make the constructor more elegant to deal with. Instead of passing numerous arguments to the constructor, you might:

* define an BookConfiguration Interface with various possible classes that implement it:
** AppBookConfiguration
** UnitTestBookConfiguration

* have ONE constructor on your Book class which expects ONE argument of type “BookConfiguration” (one little-used feature of PHP 5 is you can actually type your arguments like you can in Java and other languages):

class Book {

private $_databaseConnection;

public function __construct(BookConfiguration $configuration) {
//BookConfiguration is an Interface. when you invoke the constructor,
//you’ll actually be passing instances of either “AppBookConfiguration”
//or UnitTestBookConfiguration which are concrete classes that implement
// the BookConfiguration interface.

$this->_databaseConnection = $configuration->getDatabaseConnection()

}//Book Class Constructor

}//Book Class

A few advantages:

* addresses the possible constructor mess you outlined
* as you extend Book, and Book “requires more things to work”, you can simply still just extend your configuration class
* preserves dependency injection and the ability to supply alternate configurations based on the environment in which the class is intantiated.
* doesn’t require an extra container class to perform bootstrapping operations that are, in essence, still vital to the proper operation of your Book class.