Bad OO Design in PHP

BadDesign1.php

<?php

/**
 * @BankAccount.php
 * BankAccount is a domain object (POPO) for bank account holder.
 **/

class BankAccount {
	private $accountNumber;
	private $accountBalance;
	const interestRate = 5;

	public function __construct($accountNumber) {
		$this->accountNumber = $accountNumber;
	}
	
	// Do interest calculation business logic
	public function calculateInterest(){
		return (self::interestRate * $this->accountBalance)/100;
	}
	
	// Save money into current account business logic
	public function save($amount){
		$this->accountBalance += $amount;
	}
	
	// Withdraw money from current account business logic
	public function withdraw($amount){
		$this->accountBalance -= $amount;
	}
	
	public function getAccountNumber() {
		return $this->accountNumber;
	}
	
	public function getAccountBalance() {
		return $this->accountBalance;
	}
	
	public function setAccountBalance($accountBalance) {
		$this->accountBalance = $accountBalance;
	}
}

$account = new BankAccount("A1234");
echo $account->getAccountNumber();
$account->setAccountBalance(5000);
echo $account->getAccountBalance();
$account->save(5000);
echo $account->getAccountBalance();
$account->withdraw(5000);
echo $account->getAccountBalance();
echo $account->calculateInterest();

BadDesign2.php

<?php

class Shape {
	const CIRCLE = 1;
	const RECTANGLE = 2;
	const TYPE = 0;
	
	private $radius;
	private $width;
	private $length;
	
	public function area() {
		switch(Shape::TYPE){
			case Shape::CIRCLE:
				return M_PI * radius;
			case Shape::RECTANGLE:
				return $width * $length;
			default:
				return 0;
		}
	}

	public function createCircle($radius) {
		$this->radius = $radius;
		$this->TYPE = Shape::CIRCLE;
	}
	
	public function createRectangle($width, $length){
		$this->width = $width;
		$this->length = $length;
		$this->TYPE = Shape::RECTANGLE;
	}
}

BadDesign3.php

<?php

interface Shape {
	public function area();
}

class Rectangle implements Shape {
	private $width;
	private $length;
		
	public function __construct($width, $length){
		$this->width = $width;
		$this->length = $length;
	}
	
	public function area(){
		return $this->width * $this->length;
	}
}

class Square extends Rectangle {
	private $edge;
	
	public function __construct($edge) {
		super($edge, $edge);
		$this->edge = $edge;
	}
}

BadDesign4.php

<?php

interface Vehicle {
	function fly();
	function drive();
}

class Car implements Vehicle {
	public function fly() {
		throw new Exception("Uh oh cannot fly");
	}

	public function drive() {
		// implement drive here
	}
}

class Plane implements Vehicle {
	public function fly() {
		// implement fly here
	}

	public function drive() {
		throw new Exception("not good for driving");
	}
}

$plane = new Plane;
$plane->fly();
$plane->drive();

BadDesign5.php

<?php

interface IOutputter {
	function println($output);
}

class ConsoleOutputter implements IOutputter {
	public function println($output){
		echo $output;
	}
}

class MockOutputter implements IOutputter {
  public function println($output){
    // do nothing
  }
}

class CommandInvoker {
  public function invoke(ConsoleOutputter $outputter) {
    $outputter->println("Hello World");
  }
}

$outputter = new ConsoleOutputter;
$invoker = new CommandInvoker;
$invoker->invoke($outputter);