This plugin is based on the post Convert MySQL Tables to UTF-8 and an existing plugin by g30rg3_x. The reason I modified their code is that they will convert all tables in your database to the UTF-8 charset, but what we need is to convert WP tables, so I changed the code
"SHOW TABLES" to
"SHOW TABLES LIKE " . $table_prefix . "%", which will guarantee other tables could stay untouched. Besides, g30rg3_x's purpose was to alter the charset of old WP databases to new UTF-8 databases, but in fact we also need to change the charset after we moved our DB to a new host when the charset is not UTF-8 by default. Judging from my experience, the default charset/collation for many web hosts is
latin1_swedish_ci (I don't know why), whereas popular web-buidling systems often use
utf8_general_ci, thus we need to change the charset before all content could be normally displayed. Without PHP and
SHOW TALBES /
SHOW COLUMNS, we will need to write endless code to change all tables and all columns.
mysql> select collation('asdf'); # default collation +-------------------+ | collation('asdf') | +-------------------+ | latin1_swedish_ci | +-------------------+ 1 row in set (0.00 sec)
You can download the UTF-8 DB Converter for Wordpress.
The critical part of this plugin is:
.... $sql2 = "ALTER TABLE $table DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci"; .... $sql4 = "ALTER TABLE $table CHANGE `$field_name` `$field_name` $field_type CHARACTER SET utf8 COLLATE utf8_bin"; ....
I don't think I need to describe the installation again, but I sould warn you again about possible data lost during the conversion. Do back up early please.