php 切换背景颜色或背景图片或是切换模板是怎样实现的~

<TR style="FONT-WEIGHT: bold; FONT-STYLE: normal; BACKGROUND-COLOR: white; TEXT-DECORATION: none"    onMouseOver="this.style.backgroundColor='yellow'"onMouseOut="this.style.backgroundColor='white'">

<style>.tr1{ font-weight: bold; font-style:normal; background-color: white; text-decoration:none; }.over{ background:yellow}</style>

<script src="../js/jquery-1.5.1.min.js" type="text/javascript"></script> //记得包含jQuery插件文件<script type="text/javascript">$(function(){    $(".tr1").bind("mouseover mouseout",function(){	     $(this).toggleClass("over");	});});</script>

<TR class="tr1"><TD width="10%">姓名</TD></TR><TR class="tr1"><TD width="10%">密码</TD></TR><TR class="tr1"><TD width="10%">姓名</TD></TR><TR class="tr1"><TD width="10%">密码</TD></TR>