php selecting multiple stylesheets

Hello,
I'm trying to set up a web site. This site has multiple stylesheets,
one default stylesheet that should be used if the other is not chosen.
The second is a high contrast stylesheet and can be selected by user's
who need it. I'm also thinking of adding two more for smaller and
larger font selections. My issue is I want the high contrast sheet to
be used on all subsequent pages and on subsequent visits to the site
by user's who have selected it. I thought of using php with this and
cookies. I'm using php5 and would appreciate any suggestions, googling
has shown some examples, but none are working.
Thanks.
Dave.