www-apps/mythweb-0.28.1 is not compatible with PHP 7.1 (now stable on amd64), I get the following error: [Wed Jan 03 22:04:18.518802 2018] [php7:error] [pid 12640:tid 140369689814784] [client xx] PHP Fatal error: Cannot use $this as parameter in /var/www/localhost/htdocs/mythweb/includes/utils.php on line 218 Upstream tracked this as bug #12981 (https://code.mythtv.org/trac/ticket/12981), and a fix was cherry-picked back to the fixes/0.28 branch (https://github.com/MythTV/mythweb/commits/fixes/0.28). Either packaging an ebuild with the latest fixes/0.28 snapshot or just applying the patch to the 0.28.1 ebuild should work.
I can confirm that I saw this bug, and that upgrading to mythweb-0.28.2 solves it. See bug 648564 for ebuilds if you want them before they show up.
Now that media-tv/mythweb is updated to 29.1, mythweb should be as well. MythWeb is in maintenance mode so there's not that many changes between 28.1 and 29.1, most important is fixing compatibility with PHP 7.1+. The attached ebuild is working for me with PHP 7.2.10 (although there are some warnings that show up in the rendered pages)
Created attachment 559864 [details] mythweb-29.1.ebuild
MythWeb 31 is out and should work fine with MythTV 0.29, 30, and 31. All the changes are to fix PHP and MySQL errors. I"m using it with Apache and MythTV 30 and is working great.
Created attachment 634556 [details] MythWeb 31.0
mysql fixes/31 is now compatible with php 8, see https://github.com/MythTV/mythweb/commit/793267a8285bd13b6a0fc76702e9fd9c7810cb26. So bumping it to this version would be good. I have tested the changes and they work for me with php 8.
Created attachment 770660 [details] MythWeb 32.0 ebuild Bumped for MythWeb 32.0, I tested with PHP 8.0 and seems to be working. Has minimal changes since 31.0, so this should work with MythTV 31 also.
Created attachment 770933 [details] MythWeb 32.0 ebuild New rev of the 32.0 ebuild, fixed the php RDEPEND use flags for 8.0
Created attachment 865751 [details] MythWeb 33.1 ebuild
Added the ebuild for v33.1, includes fixes for PHP 8.1.