Keletas OO PHP klausimų

    class ImageResize{
        public $name;
        // Seni img dydžiai
        public $W, $H;
        // Nauji img dydžiai
        public $NewW = 800;
        public $NewH = 600;
        // Pakeistų paveiksliukų nuorodos
        public $path;
        // Laikini kintamieji
        public $tmp;
        public $src;
        
        public function __construct(){
            $this->src = imageCreateFromJPEG($_FILES['upload']['tmp_name']);
            list($this->W, $this->H) = getImageSize($_FILES['upload']['tmp_name']);
            $this->name = $_FILES['upload']['name'];
            $this->path = $_SERVER['DOCUMENT_ROOT'] . "/abc/upload/";
        }
        
        public function resize(){
            $this->tmp = imageCreateTrueColor($this->newW, $this->newH);
            imageCopyResampled($this->tmp, $this->src, 0, 0, 0, 0, $this->newW, $this->newH, $this->W, $this->H);
            if ( file_exists($this->path . $this->name) ){                // Jei toks failas egzistuoja
                $exts = explode(".", $this->name);            // Explodinam vardą, kad atskirti extensioną nuo failo vardo
                $this->name = $exts[0] . "_" . rand(0, 999) . "." . $exts[1];
            }
            imageJPEG($this->tmp, $this->path . $this->name, 100);
            imageDestroy($this->tmp);
            return $this->path . $this->name;
        }
        
        public function setSize($width, $height){
            $this->newW = $width;
            $this->newH = $height;
        }
        
        public function setSizeVar($max){
            if ( $this->W > $this->H ){
                $this->newW = round( $this->W * ($max / $this->W) );
                $this->newH = round( $this->H * ($max / $this->W) );
            } else {
                $this->newW = round( $this->W * ($max / $this->H) );
                $this->newH = round( $this->H * ($max / $this->H) );
            }
        }
    }