Defining constants example of wordpress

  function __construct(){
            $this->define_constants();
        }
        public function define_constants(){
            define( 'MV_SLIDER_PATH', plugin_dir_path( __FILE__ ) );
            define( 'MV_SLIDER_URL', plugin_dir_url( __FILE__ ) );
            define( 'MV_SLIDER_VERSION', '1.0.0' );
        }