/**
 * WordPress 透过 CDN 代理获取访客评论者真实 IP 地址 - 龙笑天下
 * https://www.ilxtx.com/wordpress-get-real-comment-ip.html
 */
function dr_filter_get_real_comment_ip($comment_author_IP) {
    if( is_admin() ){
        return $comment_author_IP;
    }
    
    $REMOTE_ADDR = $_SERVER['REMOTE_ADDR'];

    // 使用 CloudFlare CDN
    if ( !empty($_SERVER['HTTP_CF_CONNECTING_IP']) ) {
        $HTTP_CF_CONNECTING_IP = explode(',', $_SERVER['HTTP_CF_CONNECTING_IP']);
        if (!empty($HTTP_CF_CONNECTING_IP)) {
            $REMOTE_ADDR = trim($HTTP_CF_CONNECTING_IP[0]);
        }
    }
 
    else if (!empty($_SERVER['X_FORWARDED_FOR'])) {
        $X_FORWARDED_FOR = explode(',', $_SERVER['X_FORWARDED_FOR']);
        if (!empty($X_FORWARDED_FOR)) {
            $REMOTE_ADDR = trim($X_FORWARDED_FOR[0]);
        }
    }
 
    /*
    * Some PHP environments will use the $_SERVER['HTTP_X_FORWARDED_FOR'] 
    * variable to capture visitor address information.
    */
    else if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
        $HTTP_X_FORWARDED_FOR= explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);
        if (!empty($HTTP_X_FORWARDED_FOR)) {
            $REMOTE_ADDR = trim($HTTP_X_FORWARDED_FOR[0]);
        }
    }
 
    return preg_replace('/[^0-9a-f:., ]/si', '', $REMOTE_ADDR);
}
add_filter( 'pre_comment_user_ip', 'dr_filter_get_real_comment_ip');