Ok I got to the root of the problem, Is a little offtopic but will post here so any other user can solve this puzzle.
By default mysql doesn't have utf-8 enabled
Im using navicat and the software tell me that everything is using utf-8 but is not.
as you can see with this queries, I have a soup of character sets and collations
mysql> SHOW VARIABLES LIKE 'collation%';
+----------------------+-------------------+
| Variable_name | Value |
+----------------------+-------------------+
| collation_connection | utf8_general_ci |
| collation_database | utf8_spanish_ci |
| collation_server | latin1_swedish_ci |
+----------------------+-------------------+
3 rows in set
mysql> SHOW VARIABLES LIKE 'character_set%';
+--------------------------+-----------------------------------------------+
| Variable_name | Value |
+--------------------------+-----------------------------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | utf8 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | c:\wamp\bin\mysql\mysql5.6.12\share\charsets\ |
+--------------------------+-----------------------------------------------+
8 rows in set
Now you need to tell the server to use utf-8, edit my.cnf om linux like systems or my.ini on windows and add the following
[mysqld]
character-set-server=utf8
collation-server=utf8_general_ci
init-connect='SET NAMES utf8'
[client]
default-character-set=utf8
now restart mysql and verify
mysql> SHOW VARIABLES LIKE 'collation%';
+----------------------+-----------------+
| Variable_name | Value |
+----------------------+-----------------+
| collation_connection | utf8_general_ci |
| collation_database | utf8_general_ci |
| collation_server | utf8_general_ci |
+----------------------+-----------------+
3 rows in set
mysql> SHOW VARIABLES LIKE 'character_set%';
+--------------------------+-----------------------------------------------+
| Variable_name | Value |
+--------------------------+-----------------------------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | utf8 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | utf8 |
| character_set_system | utf8 |
| character_sets_dir | c:\wamp\bin\mysql\mysql5.6.12\share\charsets\ |
+--------------------------+-----------------------------------------------+
8 rows in set
now our server is using utf-8 and urlencode/urldecode from the serializer is working fine.
Thanks Nicolas