php获取当前域名、主机、URL、端口、参数、网址、路径、代理等

    <?php  
    //获取域名或主机地址  
    echo $_SERVER['HTTP_HOST']."<br />";  
    //获取网页地址  
    echo $_SERVER['PHP_SELF']."<br />";  
    //获取网址参数  
    echo $_SERVER["QUERY_STRING"]."<br />";  
    //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'];  
    //包含端口号的完整url  
    echo 'http://'.$_SERVER['SERVER_NAME'].':'.$_SERVER["SERVER_PORT"].$_SERVER["REQUEST_URI"];  
    //只取路径  
    $url='http://'.$_SERVER['SERVER_NAME'].$_SERVER["REQUEST_URI"];  
    echo dirname($url);  
    ?>