We know that WordPress cannot manage 4-bytes-long UTF-8 characters since the bug report Inserting a 4-byte UTF-8 character truncates data was filed on May 28, 2010. As of today (four years later) #13590 is still not fixed.

I contributed first a patch for fixing the bug on January 19, 2011 and then a plugin for fixing WP sites on May 25, 2011. They work in a very simple way:

  1. immediately before writing to the database, a 4-bytes-long UTF-8 character is converted to a safe code
  2. immediately after reading from the database, a safe code is converted to a 4-bytes-long UTF-8 character

Escaping / unescaping is very useful because PHP, which can manage 4-bytes-long UTF-8 characters, will manage them and MySQL, which cannot manage them (*), will manage a safe code instead.

There are only a couple of issues with this method, though. If a string contains some 4-bytes-long UTF-8 characters then

  1. the length of the string in PHP will appear lower than in MySQL
  2. the order of the string in PHP will be different from MySQL

For me, they are minor problems, when compared to the peace of mind of being able to paste or edit whatever UTF-8 text I might come up with.

As I said, #13590 is still not fixed after 4 years. Meanwhile,

  1. 2010-05-28 06:53 – #13590 opened – sardisson filed Inserting a 4-byte UTF-8 character truncates data
  2. 2010-10-27 12:28 – #13590 – Component changed from General to Charset – Milestone changed from Awaiting Review to Future Release
  3. 2010-12-31 13:21 – #13590 closed – Resolution set to invalid – Status changed from new to closed
  4. 2011-01-13 02:55 – #13590 – Milestone Future Release deleted
  5. 2011-01-19 09:32 – #13590 reopened – Component changed from Charset to Database – Keywords utf8 added – Resolution invalid deleted – Status changed from closed to reopened – Summary changed from Inserting a tetragram (SMP/Plane 1) character truncates post fields to Inserting a 4-byte UTF-8 character truncates data – Version changed from 2.9.2 to 3.0.4
  6. 2011-01-19 09:57 – #13590 – Milestone set to Awaiting Review
  7. 2011-01-19 21:40 – #13590 – Attachment wp-db-utf8-patch.diff​ added (my patch)
  8. 2011-05-25 – I published my plugin
  9. 2011-05-25 21:43 – #13590 – Keywords has-patch added – Type changed from defect (bug) to enhancement
  10. 2012-07-11 04:26 – #21212 opened – Gary Pendergast (pento) filed MySQL tables should use utf8mb4 character set, basically suggesting to take advantage of utf8mb4, which is how MySQL developers fixed their bug. (*)
  11. 2012-08-08 06:49 – #13590 – Milestone changed from Awaiting Review to 3.5
  12. 2012-08-29 01:54 – #13590 closed – Keywords utf8 removed – Milestone 3.5 deleted – Resolution set to maybelater – Status changed from reopened to closed – Version changed from 3.0.4 to 2.9.2
  13. 2013-02-18 21:36 – #13590 – Duplicated by #23495
  14. 2012-07-11 04:28 – #21212 – Attachment 21212-utf8mb4.diff​ added
  15. 2012-07-11 04:29 – #21212 – Keywords has-patch added
  16. 2012-07-11 11:22 – #21212 – Related to #13590
  17. 2012-07-18 06:52 – #21212 – Attachment 21212-utf8mb4.2.diff​ added
  18. 2012-07-30 – Mathias Bynens published How to support full Unicode in MySQL databases
  19. 2012-08-07 04:13 – #21212 – Attachment 21212-utf8mb4.3.diff​ added
  20. 2012-08-07 05:06 – #21212 – Milestone changed from Awaiting Review to 3.5
  21. 2012-08-07 06:39 – #21212 – Keywords commit added
  22. 2012-08-29 01:54 – #21212 closed – Milestone 3.5 deleted – Resolution set to maybelater – Status changed from new to closed
  23. 2012-10-09 05:24 – #21212 reopened – Keywords has-patch commit removed – Resolution maybelater deleted – Status changed from closed to reopened
  24. 2012-10-09 06:56 – #21212 – Milestone set to Awaiting Review
  25. 2014-04-07 – Gary Pendergast (pento) published WordPress and UTF-8
  26. 2014-04-22 02:08 – #21212 – Duplicated by #27961
  27. 2014-06-11 – Andrew Nacin (nacin) and core WP developers started thinking about a fix.
  28. 2014-08-22 15:47 – #21212 – Duplicated by #29322
  29. 2014-09-28 13:20 – #21212 – Duplicated by #29773
  30. 2014-10-04 18:49 – #21212 – Duplicated by #29857

FWIW, since I’ve been using my plugin I forgot about WordPress and UTF-8.