PHP获得IP地址

function getIp() {
    $ip = '0.0.0.0';

    if(isset($_SERVER['HTTP_X_FORWARDED_FOR']))
        $ip = $_SERVER ['HTTP_X_FORWARDED_FOR'];
    else if(getenv('HTTP_X_FORWARDED_FOR'))
        $ip = getenv('HTTP_X_FORWARDED_FOR');

    if (isset($_SERVER['HTTP_CLIENT_IP']))
        $ip = $_SERVER['HTTP_CLIENT_IP'];
    else if (getenv('HTTP_CLIENT_IP'))
        $ip = getenv('HTTP_CLIENT_IP');

    if (isset ($_SERVER['REMOTE_ADDR']))
        $ip = $_SERVER['REMOTE_ADDR'];
    else if (getenv('REMOTE_ADDR'))
        $ip = getenv('REMOTE_ADDR');

    return addslashes($ip);
}