function getsiteurl() 
{ 
global $_SCONFIG; 

if(empty($_SCONFIG['siteallurl'])) 
{ 
$uri = $_SERVER['REQUEST_URI']?$_SERVER['REQUEST_URI']:($_SERVER['PHP_SELF']?$_SERVER['PHP_SELF']:$_SERVER['SCRIPT_NAME']); 
return shtmlspecialchars('http://'.$_SERVER['HTTP_HOST'].substr($uri, 0, strrpos($uri, '/')+1)); 
} 
else 
{ 
return $_SCONFIG['siteallurl']; 
} 
}

global $_SCONFIG; //定义全局变量$_SCONFIG($_SCONFIG其实是个数组var,在common.php中有定义)

if(empty($_SCONFIG['siteallurl'])) //判断$_SCONFIG['siteallurl']变量是否为空

$uri = $_SERVER['REQUEST_URI']?$_SERVER['REQUEST_URI']:($_SERVER['PHP_SELF']?$_SERVER['PHP_SELF']:$_SERVER['SCRIPT_NAME']);

//将$_SERVER['REQUEST_URI'];$_SERVER['PHP_SELF'];$_SERVER['SCRIPT_NAME']通过三目运算后把结果给$url

//$_SERVER也是数组,你可以打印一下,就知道干吗用的了.这里只涉及到三个数组元素

//$_SERVER['REQUEST_URI']; //REQUEST_URI:/mysite/->站点目录?

//$_SERVER['PHP_SELF']; //PHP_SELF:/mysite/index.php->当前正在执行脚本的文件名

//$_SERVER['SCRIPT_NAME']; //SCRIPT_NAME:/mysite/index.php->包含当前脚本的路径