Display image if variable set to true

I'm making a website for a friend and am wondering about the best way to do something.

It's a flat site and he wants the ability to disable a banner advert without editing all the pages. I thought the best way to do this is have a file somewhere with a variable set to true then have a bit of php in the <div> on his site that will only display the ad if this variable is set to true.

Am i right in thinking i can put the following in the top of every page

and then something like the following in the div that holds the banner

The problem i'm having is that the image is constantly displaying and i can't get it to bugger off no matter what the $adswitch variable is set to.

Thanks

re: Display image if variable set to true

Silly question but will adding an else fix it?

re: Display image if variable set to true

I am assuming the $adswitch variable is creates in 'ad_switch.php'. This variable goes out of scope as soon as 'ad_switch.php' ends. Therefore your statement[PHP] <?php if ($adswitch = true) { image goes here ;} ?> [/PHP] is instaniating a new variable which (and this catches the unwary out) is TRUE by default.