用php实现，打开哪个页面哪个页面就有默认的样式

<?php $f=$_SERVER[‘PHP_SELF‘];?>
<div class="nav">
	<div class="navcon">
    	<ul>
        	<li <?= $f==‘/index.php‘ ? ‘class="navhome"‘ :‘‘?>><a href="#">首页</a></li>
            <li <?= $f==‘/news.php‘ ? ‘class="navhome"‘ :‘‘?>><a href="#">新闻中心</a></li>
            <li <?= $f==‘/about.php‘ ? ‘class="navhome"‘ :‘‘?>><a href="#">关于我们</a></li>
            <li <?= $f==‘/pro.php‘ ? ‘class="navhome"‘ :‘‘?>><a href="#">精品工程</a></li>
            <li <?= $f==‘/zzry.php‘ ? ‘class="navhome"‘ :‘‘?>><a href="#">资质荣誉</a></li>
            <li <?= $f==‘/woker.php‘ ? ‘class="navhome"‘ :‘‘?>><a href="#">员工风采</a></li>
            <li <?= $f==‘/guestbook.php‘ ? ‘class="navhome"‘ :‘‘?>><a href="#">在线留言</a></li>
            <li <?= $f==‘/job.php‘ ? ‘class="navhome"‘ :‘‘?>class="navlast"><a href="job.php">诚聘英才</a></li>
        </ul>
    </div>
</div>