用PHP实现换肤

用PHP其实也可以实现简单的“换肤”，其实就是换CSS（当然不可能做到象asp.net 2.0那样厉害拉），
但有时也可以凑合着使用，先要准备几个CSS
style/default.css
body { font-family: arial, verdana; font-size: small; margin: 0px; }
.box { background: red; }
.box-title { text-align: center; color: white; font-weight: bold; }
.box-content { background: white; font-size: xx-small; padding:10px;}
.menu { margin: 5px; }
.menu-active { margin: 2px; padding:5px; background: black; }
.menu-active a { text-decoration: none; color: white; font-weight: bold; }
.menu-inactive { margin: 2px; padding:5px; background: #ccc; }
.menu-inactive a { text-decoration: none; }

styles/black_and_white.css
body { font-family: arial, verdana; font-size: small; margin: 0px; }
.box { background: #eee; border: 1px solid black; }
.box-title { background: white; text-align: center; font-weight: bold; }
.box-content { background: white; font-size: xx-small; padding:10px;}
.menu { margin: 5px; }
.menu-active { margin: 2px; padding:5px; background: black; }
.menu-active a { text-decoration: none; color: white; font-weight: bold; }
.menu-inactive { margin: 2px; padding:5px; background: #ccc; }
.menu-inactive a { text-decoration: none; }

index.php