[fysiks]

The error is because the symbol (aka variable) is undefined, just as the error says. According to the code you included in your post, the variable definition and how it gets its value is commented out.

P.S. When including code in your post on the forums, you should use either [code][/code] or [php][/php] tags around the code so that it gets formatted as code making it easier to read. I also recommend using the [code][/code] for the compiler console output to make it easier to read also.