通过php<code>setcookie()</code>第三个参数设置cookie过期时间来删除cookie，代码如下：

if($_COOKIE['username']!=""&&$_COOKIE[‘pwd’]!=""){
        if(isset($_GET[cookie])){
                  setcookie("username","",time()-1);
                  setcookie("pwd","",time()-1);
                  setcookie("IP","",time()-1);
                  echo"<script>alert("cookie已经删除")；location.href="index.php"</script>"
        }
}