php try and catch

<?php

	class InputException extends Exception
	{
		private $_invalidWarpFactor;

		public function __construct( $message , $code, $factor )
		{
			parent::__construct( $message , $code );
			$this->_invalidWarpFactor = $factor;
		}

		public function getInvalidWarpFactor()
		{
			return $this->_invalidWarpFactor;
		}
	}  // End of class Exception


	class FuelException extends Exception
	{
		private $_remainingFuel;

		public function __construct( $message , $code , $remainingFuel )
		{
			parent::__construct( $message , $code );
			$this->_remainingFuel = $remainingFuel;
		}

		public function getRemainingFuel()
		{
			return $this->_remainingFuel;
		}


	} //  End of class FuelException


	class WarpDrive
	{
		static private $_dilithiumLevel = 10;

		public function setWarpFactor( $factor )
		{
			if( $factor < 1 )
			{
				throw new InputException( "Warp need to be atleast 1", 1 , $factor );
			}

			else if( $factor > 9 )
			{
				throw new InputException( "Warp Factor exceeds drive specification" , 2 , $factor );
			}

			else if( WarpDrive::$_dilithiumLevel < $factor )
			{
				throw new FuelException( "Insufficient fuel" , 3  , WarpDrive::$_dilithiumLevel );
			}

			else
			{
				WarpDrive::$_dilithiumLevel -= $factor;
				echo "<p>Now traveling at a warp factor $factor</p>";
			}
		}
	}  // End of class WarpDrive

	class ChiefEngineer
	{
		public function doWarp( $factor )
		{
			$wd = new WarpDrive();
			$wd->setWarpFactor($factor);
		}
	}

	class Captain
	{
		public function newWarpOrder( $factor )
		{
			$ce = new ChiefEngineer();

			try
			{
				$ce->doWarp( $factor );
			}

			catch( InputException $e )
			{
				echo "<p>Captain's log: Warp factor " . $e->getInvalidWarpFactor() . "? I must be losing my mind ...</p>";
			}

			catch( FuelException $e )
			{
				echo "<p>Captain log: I'm getting fuel problem from the warp engine. It says '" . $e->getMessage();
				echo "' . we have " . $e->getRemainingFuel() . "dilithium left. I guess w're not going anywhere</p>";
			}

			catch( Exception $e )
			{
				echo "<p>Captain's log: something else happend , I don't know what. The message is '" . $e->getMessage() ."'<p>";
			}

		}
	} // End of class Captain

	$c = new Captain();
	$c->newWarpOrder(5);
	$c->newWarpOrder(-1);
	$c->newWarpOrder(12);
	$c->newWarpOrder(4);
	$c->newWarpOrder(9);


?>