/**

     * 判断是否为https

     * @return bool 是https返回true;否则返回false

     */

    function is_https() {

        if ( !empty($_SERVER['HTTPS']) && strtolower($_SERVER['HTTPS']) !== 'off') {

            return true;

        } elseif ( isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && $_SERVER['HTTP_X_FORWARDED_PROTO'] === 'https' ) {

            return true;

        } elseif ( !empty($_SERVER['HTTP_FRONT_END_HTTPS']) && strtolower($_SERVER['HTTP_FRONT_END_HTTPS']) !== 'off') {

            return true;

        }else{

            return false;

        }

    }

//获取域名或主机地址

echo $_SERVER['HTTP_HOST']."<br>"; #localhost

//获取网页地址

echo $_SERVER['PHP_SELF']."<br>"; #/blog/testurl.php

//获取网址参数

echo $_SERVER["QUERY_STRING"]."<br>"; #id=5

//获取用户代理

echo $_SERVER['HTTP_REFERER']."<br>";

//获取完整的url

echo 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];

echo 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF'].'?'.$_SERVER['QUERY_STRING'];

#http://localhost/blog/testurl.php?id=5

//包含端口号的完整url

echo 'http://'.$_SERVER['SERVER_NAME'].':'.$_SERVER["SERVER_PORT"].$_SERVER["REQUEST_URI"];

#http://localhost:80/blog/testurl.php?id=5

//只取路径

$url='http://'.$_SERVER['SERVER_NAME'].$_SERVER["REQUEST_URI"];

echo dirname($url);

#http://localhost/blog