some problem about tinymce module

I want to use the PHP Control in visibility of the tinymce module.
The PHP code I use:

<?php
if($format == 3 || $node->format == 3)
return true;
else
return false;
?>

When the INPUT FORMAT equal 3 (the value of FULL HTML), the tinymce module will be visible.But, it doesn't work.

I think the problem is the variable, $format [$node->format] in PHP code.
Could someone help me? Which variable is right to the INPUT FORMAT?