分享一个php获取客户端IP的函数：

function getIp()
{
    $realip = '';
    $unknown = 'unknown';
    
    if (isset($_SERVER)) {
        if (isset($_SERVER['HTTP_X_FORWARDED_FOR']) && ! empty($_SERVER['HTTP_X_FORWARDED_FOR']) && strcasecmp($_SERVER['HTTP_X_FORWARDED_FOR'], $unknown)) {
            $arr = explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
            foreach ($arr as $ip) {
                $ip = trim($ip);
                if ($ip != 'unknown') {
                    $realip = $ip;
                    break;
                }
            }
        } else if (isset($_SERVER['HTTP_CLIENT_IP']) && ! empty($_SERVER['HTTP_CLIENT_IP']) && strcasecmp($_SERVER['HTTP_CLIENT_IP'], $unknown)) {
            $realip = $_SERVER['HTTP_CLIENT_IP'];
        } else if (isset($_SERVER['REMOTE_ADDR']) && ! empty($_SERVER['REMOTE_ADDR']) && strcasecmp($_SERVER['REMOTE_ADDR'], $unknown)) {
            $realip = $_SERVER['REMOTE_ADDR'];
        } else {
            $realip = $unknown;
        }
    } else {
        if (getenv('HTTP_X_FORWARDED_FOR') && strcasecmp(getenv('HTTP_X_FORWARDED_FOR'), $unknown)) {
            $realip = getenv("HTTP_X_FORWARDED_FOR");
        } else if (getenv('HTTP_CLIENT_IP') && strcasecmp(getenv('HTTP_CLIENT_IP'), $unknown)) {
            $realip = getenv("HTTP_CLIENT_IP");
        } else if (getenv('REMOTE_ADDR') && strcasecmp(getenv('REMOTE_ADDR'), $unknown)) {
            $realip = getenv("REMOTE_ADDR");
        } else {
            $realip = $unknown;
        }
    }
    
    $realip = preg_match("/[\d\.]{7,15}/", $realip, $matches) ? $matches[0] : $unknown;
    
    return $realip;
}