Using if statement in dynamic stylesheet?

I want to give the option of either having a fixed header or not..

#header {
	<?php if ( moon_get_option('example_checkbox') ) { ?>
    position: <?php echo moon_get_option('example_checkbox', 'fixed' ); ?>;
    width: 100%;
    z-index: 1;
	<?php } ?>
}

I am slowly learning php, and I know that I can say if example_checkbox is set to true then echo the text “fixed”, I am pretty sure that’s the best way to do it, but I don’t know how to say that in php yet, so if you have any idea I would really appreciate it.

This would be very powerful and could really help my theme development if I could get some insight on using if statements with dynamic CSS..

I searched for an answer for this and couldn’t find much.

http://wordpress.org/extend/plugins/options-framework/