Could you tell me how to make it quality code?<?phpclass Game {    public function __construct() {        session_start();    }    public function play(){        return '<input type=button value=Play onclick=window.location = \'?play=1\'>';    }    public function start($msg=null) {        unset($_SESSION['bees']);        $bee = new Bee();        $bee->setType('queen');        $this->addBee($bee,1);        $bee->setType('worker');        $this->addBee($bee,5);        $bee->setType('drone');        $this->addBee($bee,8);        if($msg)            return $msg;        else {            var_dump($_SESSION['bees']); // debug            return 'Game started <input type=button value=Hit onclick=window.location = \'?hit=1\'>';        }    }    public function hit() {        $msg = '';        if($_SESSION['bees'])            $rd = array_rand($_SESSION['bees'],1);        else            $this->start('Game will start again');        $_SESSION['bees'][$rd]['lifespan'] = $_SESSION['bees'][$rd]['lifespan'] - $_SESSION['bees'][$rd]['hit'];        if($_SESSION['bees'][$rd]['lifespan']<1) {            $_SESSION['bees'][$rd]['bees'] -=1;            $_SESSION['bees'][$rd]['lifespan'] = $_SESSION['bees'][$rd]['life'];            switch($rd)            {                case 'queen': $msg .= $this->start('Game start again, the Queen is dead.'); break;                default: $msg .= 'One \'' . $rd . '\' is gone';            }        }        if($_SESSION['bees'][$rd]['bees']<1){            unset($_SESSION['bees'][$rd]);            $msg = 'The \'' . $rd . '\' team is gone';        }        var_dump($_SESSION['bees']); // debug        return '<input type=button value=Hit onclick=window.location = \'?hit=1\'> ' . $msg;    }    public function addBee(Bee $newbee, $number = 1) {        $tipo = $newbee->getType();        $bee = $newbee->get();        $_SESSION['bees'][$tipo] = $bee;        $_SESSION['bees'][$tipo]['bees'] = $number;        $_SESSION['bees'][$tipo]['life'] = $newbee->getLifespan($tipo);    }}class Bee{protected $_type = null;protected $_types = array(    'queen' => array(    'hit' => 8,    'lifespan' => 100    ),    'worker' => array(    'hit'   =>  10,    'lifespan' => 75    ),    'drone' => array(    hit'    =>  12,    'lifespan' => 50    )    );    public function setHit(){}    public function setLifespan(){}    public function addNewType(){}    protected function _set_hit(){}    protected function _set_lifespan(){}    protected function _add_new_type(){}    public function getLifespan($type){        if(array_key_exists($type,$this->_types))            return $this->_types[$this->_type]['lifespan'];        else            throw new Exception('The Bee need to be a Queen, Worker or Drone');    }    public function getTypes() {        return $this->_types;    }    public function getType() {        return $this->_type;    }    public function setType($type) {        if(array_key_exists($type,$this->_types))            $this->_type = $type;        else            throw new Exception('The Bee need to be a Queen, Worker or Drone');    }    public function get() {        return $this->_types[$this->_type];    }}?><html><head><title>play Bee</title></head><body>    <?php                                                       $game = new Game();        if(isset($_GET['play']) && $_GET['play']) {            echo $game->start();        } else if(isset($_GET['hit']) && $_GET['hit']) {            echo $game->hit();        } else {            echo $game->play();        }    ?></body></html>
Basic bee game labeled as messy
php;game