in addition, FusionBB is rather dated and may not work with a recent PHP 5 version. there is also no documented support for PHP 7 compatibility at all.
It was working fine with php 5.3. We have however just migrated our last forum out of Fusionbb as it was getting dated & because it was likely to fail eventually on future versions. I was one of the last (non-tech) admins on their site when it closed. Mostly deleting spam as it was so quiet! The major feature for us was the gallery feature. It didn't sit outside of the main forum. It was totally integrated. You could turn a forum into a gallery & visa versa very easily. Posts could be moved from forum to gallery & v.v. too.
