WordPress 4.2 was released this week, and it includes full support for emoji, including in post titles and URLs. To take advantage of that, I published a post that used the 💥 emoji (https://s.w.org/images/core/emoji/72x72/1f4a5.png, in case it get's stripped out) in the title and URL, however Piwik failed to track any views of the post because piwik.php is returning a 400 - bad request status code. I confirmed against two other tracking systems that there were views to the post that should've been captured by Piwik.

Is this a problem with the DB encoding (utf8 vs utf8mb4) or an issue in the PHP handling of the title and URL inputs when they include extended UTF-8 characters?