generate documentation from config.sample.php

admin_manual/configuration_server/config_sample_php_parameters.rst

@@ -1242,6 +1242,35 @@ encryption in MySQL or specify a custom wait timeout on a cheap hoster.
 sqlite3 journal mode can be specified using this configuration parameter -
 can be 'WAL' or 'DELETE' see for more details https://www.sqlite.org/wal.html
 
+::
+
+	'mysql.utf8mb4' => false,
+
+If this setting is set to true MySQL can handle 4 byte characters instead of
+3 byte characters
+
+MySQL requires a special setup for longer indexes (> 767 bytes) which are
+needed:
+
+[mysqld]
+innodb_large_prefix=true
+innodb_file_format=barracuda
+innodb_file_per_table=true
+
+Tables will be created with
+ * character set: utf8mb4
+ * collation:     utf8mb4_bin
+ * row_format:    compressed
+
+See:
+https://dev.mysql.com/doc/refman/5.7/en/charset-unicode-utf8mb4.html
+https://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_large_prefix
+https://mariadb.com/kb/en/mariadb/xtradbinnodb-server-system-variables/#innodb_large_prefix
+http://www.tocker.ca/2013/10/31/benchmarking-innodb-page-compression-performance.html
+http://mechanics.flite.com/blog/2014/07/29/using-innodb-large-prefix-to-avoid-error-1071/
+
+WARNING: EXPERIMENTAL
+
 ::
 
 	'supportedDatabases' => array(