Complex-Number calculation

Complex.php

<?php

class Complex {

	/**
	 * Real
	 * @var double
	 */
	private $real;

	/**
	 * Imag
	 * @var double
	 */
	private $imag;

	/**
	 * Add Const
	 * @var static
	 */
	const ADD = 0;

	/**
	 * Subtract Const
	 * @var static
	 */
	const SUBTRACT = 1;

	/**
	 * Multiply Const
	 * @var static
	 */
	const MULTIPLY = 2;

	/**
	 * Divide Const
	 * @var static
	 */
	const DIVIDE = 3;


	/**
	 * Sets a complex number
	 *
	 * @param double $real
	 * @param double $imag
	 * @return Complex
	 */
	public function __construct($real = null, $imag = null) {

		$this->real = $real;
		$this->imag = $imag;

		return $this;
		
	}
	
	/**
	 * Real getter
	 * @return double
	 */
	public function getReal() {
		
		return $this->real;
		
	}

	/**
	 * Imag getter
	 * @return double
	 */
	public function getImag() {
		
		return $this->imag;
		
	}

	/**
	 * Add method
	 * @param Complex $a
	 * @param Complex $b
	 * @return Complex
	 */
	private static function add(Complex $a, Complex $b) {
		
		$real = $a->getReal() + $b->getReal();
		$imag = $a->getImag() + $b->getImag();
		return new Complex($real, $imag);
		
	}

	/**
	 * Subtract Method
	 * @param Complex $a
	 * @param Complex $b
	 * @return Complex
	 */
	private static function subtract(Complex $a, Complex $b) {
		
		$real = $a->getReal() - $b->getReal();
		$imag = $a->getImag() - $b->getImag();
		return new Complex($real, $imag);
		
	}

	/**
	 * Multiply Method
	 * @param Complex $a
	 * @param Complex $b
	 * @return Complex
	 */
	private static function multiply(Complex $a, Complex $b) {

		$real = $a->getReal() * $b->getReal() - $a->getImag() * $b->getImag();
		$imag = $a->getReal() * $b->getImag() - $a->getImag() * $b->getReal();

		return new Complex($real, $imag);
	}

	/**
	 * Divide Method
	 * @param Complex $a
	 * @param Complex $b
	 * @throws Exception
	 * @return Complex
	 */
	private static function divide(Complex $a, Complex $b) {

		if ($b->getReal() != 0 && $b->getImag() != 0) {
			$real = ($a->getReal() * $b->getReal() + $a->getImag() * $b->getImag()) / ($b->getReal() * $b->getReal() + $b->getImag() * $b->getImag());
			$imag = ($a->getImag() * $b->getReal() - $a->getReal() * $b->getImag()) / ($b->getReal() * $b->getReal() + $b->getImag() * $b->getImag());
			return new Complex($real, $imag);
		}

		else throw new Exception("Division durch Null nicht erlaubt");
	}

	/**
	 * Calculate Method
	 * @param Complex $a
	 * @param Complex $b
	 * @param const $operator
	 * @return Complex
	 */
	public static function calculate(Complex $a, Complex $b, $operator) {
			
		switch ($operator) {

			case static::ADD:
				return static::add($a, $b);
				break;

			case static::SUBTRACT:
				return static::subtract($a, $b);
				break;
					
			case static::MULTIPLY:
				return static::multiply($a, $b);
				break;

			case static::DIVIDE:
				return static::divide($a, $b);
				break;

			default:
				return static::add($a, $b);
				break;
		}

	}
	
	public function __toString() {
		
		return $this->getReal() . " + " . $this->getImag() . "i"; 
		
	}

}