Modernizing Legacy Applications in PHP

The replacement process

The next step, then, is to remove all use of new keyword from our non-Factory classes, and inject the necessary dependencies instead. We will also use Factory objects as needed to deal with repeated creation dependencies. This is the general process we will follow:

1. Find a class with the new keyword in it. If the class is already a Factory, we can ignore it and move on.
2. For each one-time creation in the class:
   • Extract each instantiation to a constructor parameter.
   • Assign the constructor parameter to a property.
   • Remove any constructor parameters and class properties that are used only for the new call.
3. For each repeated creation in the class:
   • Extract each block of creation code to a new Factory class.
   • Create a constructor parameter ...