PHP获取客户端和服务器IP地址

/**
 * 获取客户端IP地址
 * @return string
 */
function get_client_ip() { 
    if(getenv('HTTP_CLIENT_IP')){ 
        $client_ip = getenv('HTTP_CLIENT_IP'); 
    } elseif(getenv('HTTP_X_FORWARDED_FOR')) { 
        $client_ip = getenv('HTTP_X_FORWARDED_FOR'); 
    } elseif(getenv('REMOTE_ADDR')) {
        $client_ip = getenv('REMOTE_ADDR'); 
    } else {
        $client_ip = $_SERVER['REMOTE_ADDR'];
    } 
    return $client_ip; 
}   
/**
* 获取服务器端IP地址
 * @return string
 */
function get_server_ip() { 
    if (isset($_SERVER)) { 
        if($_SERVER['SERVER_ADDR']) {
            $server_ip = $_SERVER['SERVER_ADDR']; 
        } else { 
            $server_ip = $_SERVER['LOCAL_ADDR']; 
        } 
    } else { 
        $server_ip = getenv('SERVER_ADDR');
    } 
    return $server_ip; 
}
//该片段来自于http://outofmemory.cn