I think emoji are killing my WordPress site… How can I debug?

I have had a rather frustrating last couple of days… after quite a bit of trial and error, I have come to the suspicion that emoji are killing my WordPress installation. Specifically, emoji in the settings of my theme.

In retrospect, I can see that even trying to use emoji was a bit of a risky proposition. As I understand it, they are not officially a part of the UTF-8 character set.

For the time being, I have tried to carefully go back through all of my theme settings and eliminate any use of emoji anywhere. But now, I would like to find out exactly how they are breaking WordPress and where. Trouble is, I’m not familiar with PHP beyond the basics I’ve needed to pick up for theme customization.

Where should I begin to debug this problem?

This is a limitation of MySQL’s UTF-8 implementation: it supports just a limited set of valid UTF-8 characters. You can convert your database to utf8mb4, and emojis will work. But there may be other side effects.

See ticket #21212 for details.