getcwd();
// /mnt/qa/test
dirname(__FILE__);
// /mnt/qa/test

$_SERVER['HTTP_HOST']; 
 //daxiangtravel.com

$_SERVER['PHP_SELF'];
// /qa/test/index.php

$_SERVER["QUERY_STRING"];
// v=433
获取用户代理

$_SERVER['HTTP_REFERER'];
// http://daxiangtravel.com/qa/test/index.php?v=433

 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI']; 
// http://daxiangtravel.com/qa/test/index.php?v=433
 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF'].'?'.$_SERVER['QUERY_STRING'];
// http://daxiangtravel.com/qa/test/index.php?v=433

$url='http://'.$_SERVER['SERVER_NAME'].$_SERVER["REQUEST_URI"];
echo dirname($url);
// http://daxiangtravel.com/qa/test

 'http://'.$_SERVER['SERVER_NAME'].':'.$_SERVER["SERVER_PORT"]
.$_SERVER["REQUEST_URI"];
// http://daxiangtravel.com:80/qa/test/index.php?v=433