$_SERVER['HTTP_HOST'] //获取域名或主机地址
$_SERVER['SERVER_NAME'] //获取域名或主机地址,但不包括端口号
$_SERVER['SERVER_PORT'] //获取端口号
$_SERVER['HTTP_HOST'] = $SERVER_PORT['SERVER_NAME'].":".$_SERVER['SERVER_PORT']
//获取地址栏的完整路径
$url="http://".$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];
//或者
$url="http://".$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF']."?".$_SERVER['QUERY_STRING']
$_SERVER['PHP_SELF'] //返回文件路径
$_SERVER['QUERY_STRING'] //获取请求的参数。?后面的部分,不包括?