Thanks a lot Ken.
When I managed to convert all the tables in the DB from utf8_unicode_ci to utf8mb4_unicode_ci, problem solved.
It seems that we could draw a conclusion: the breakdown was caused by the character set of data tables.
Thank you again Ken for your great help.
Zhang
Those scripts didn't work for my website. so many error message, and even enabling debugging didn't show any thing else. Also, Permission Denied message, etc, etc.
I went to phpmyadmin, and selected all tables (The half was already utf8mb4_unicode_ci, but the other was still utf8_unicode_ci), and then changed to utf8mb4_unicode_ci in operation function.
It was really easier to deal with Unix shell scripts.
