Plugin Detection with PHP?

Is there a way to use PHP to tell whether a user's browser has a particular plugin? I thought that the $HTTP_ACCEPT variable might have this type of information, but in a little test that I have done, it just returns "*/*". I know that this can be done using Javascript, but as this can be turned off by the user etc, it seemed as though it would be more reliable to do it server side (if it is possible). Thanks Andy Clarke ------------------------------------------------ Andy Clarke 78 West Kensington Court, Edith Villas, London, England W14 9AB phone: 44 (0)20 7602 3382 mobile: 07947 418177 Freelance Lingo/PHP Programmer andy@kinonet.com ------------------------------------------------