SOLID Sample Code

DIP.php

<?php
class FooControllerConventional
{
	function indexView() {
		$model = new FooModel();
		$viewData = $model->fetchAll();
		$view = new FooView();
		$view->render($viewData);
	}
}

class FooControllerDI
{
	private $_model;
	private $_view;
	
	function __construct(FooModel $model, FooView $view) {
		$this->_model = $model;
		$this->_view = $view;
	}
	
	function indexView() {
		$viewData = $this->_model->fetchAll();
		$this->_view->render($viewData);
	}
}

interface ViewServiceInterface {
	function render($viewData);
	//... Other required methods
}

interface ModelServiceInterface {
    function fetchAll();
    // ... Other required methods
}

class FooControllerDIP
{
	private $_model;
	private $_view;
	
	function __construct(ModelServiceInterface $model, 
						ViewServiceInterface $view) {
		$this->_model = $model;
		$this->_view = $view;
	}
	
	function indexView() {
		$viewData = $this->_model->fetchAll();
		$this->_view->render($viewData);
	}
}

ISP.java

public class UserModel {
    public String doLogin(String userID, String password) { 
        /* ... */ 
        return "authToken";
    }
    public Boolean authenticate(String authToken) {
        /* ... */ 
        return true;
    }
}

public interface ILoginService {
    String doLogin(String userID, String password);
}

public interface IAuthenticationService {
    Boolean authenticate(String authToken);
}


public class UserModel implements ILoginService, IAuthenticationService {
    @Override
    public String doLogin(String userID, String password) { 
        /* ... */ 
        return "authToken";
    }
    @Override
    public Boolean authenticate(String authToken) {
        /* ... */ 
        return true;
    }
}

LSP.cs

using System;

namespace ScratchConsoleApp
{
    class Duck {
        public void Fly() { /* ... */ }
    }

    class DecoyDuck : Duck {
        public new void Fly()
        {
            throw new Exception("Decoy ducks don't fly.");
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var duck = new DecoyDuck();
            duck.Fly();
        }
    }
}

LSP.java

//LSP Violation Example - Covariant parameter
//BarModel extends FooModel

public class FooView {
    void display(FooModel foo) { /* ... */ }
}


public class BarView extends FooView {
    void display(BarModel foo) { /* ... */ }
}

LSP.py

class FooMapper:
    """Returns a set."""
    def fetchAll(self):
        return ['a', 'b', 'c']
	
class BarMapper (FooMapper):
    """Returns a tupple."""
    def fetchAll(self):
        return ('a', 'b', 'c')
		
foo = FooMapper()
bar = BarMapper()
fooItems = foo.fetchAll()
barItems = bar.fetchAll()

print fooItems, barItems