Help understanding/debugging the following script:

Hi all. If you look at the code below, the return() does not produce any output. No errors were displayed on screen before I added 'error_reporting(E_ALL);'. (Error message: Notice: Undefined variable: this in /oop/test1/index.php on line 35, commented on below) Trying to echo/print ordinary text or variables works fine. I have some experience coding PHP scripts, but are new on how-to use/write OOP scripts. (Sample found at: http://www.purephotoshop.com/view.php?id=71) Here's the Code: <?php error_reporting(E_ALL); class Bike { var $num_speeds, $speed; var $rotation; var $running = FALSE; // You can set default values for properties, these values must be constant // Change speed method function change_speed( $increment = TRUE ) { // ... } // Pedal and brake methods function pedal() { // ... } function brake() { // ... } // Turn method function turn( $angle ) { // ... } } // Inside the change_speed() method if( !$this->running ) // This is line 35 { return; } if( $increment && $this->speed != $this->num_speeds ) { $this->speed++; return; } if( $this->speed != 1 ) { $this->speed--; } ?> I will be thankful for any help/hints that leads to a solution. If anymore info are needed, please let me know. Regards, Martin