I am trying to install the plugin "HTML in Posts", when I try to activate I get this error
[
attachment=37076]
I am using myBB 1.8.7 and MySQLi 5.7.13
I believe you are talking about this plugin
https://mods.mybb.com/view/html-in-posts
That is because that plugin is not supported on MyBB 1.8
In MyBB 1.8, there is no need to install any extra plugin to add html in posts. You can find settings to turn on HTML inside forum settings i.e. forum's settings under Miscellaneous Options.
Regards
WallBB