Code: Select all
Incorrect string value: '\xF0\x9F\x98\x84' for column 'post_text' at row 1 
Incorrect string value: '\xF0\x9F\x98\x81' for column 'draft_message' at row 1 
then you probably inserted an "emoji" character (like a smiley face) from your tablet or phone's on-screen keyboard. The database cannot handle these special four-byte characters, yet.
We are investigating a fix for this.
Update: phpBB3 version 3.2 should be able to handle emoji characters. We're currently running phpBB 3.0, but hope to upgrade to 3.1 early in 2016, and to 3.2 as soon as we can (it is not yet released).