Did you try to replace localhost with 127.0.0.1?

edit (added question): Is the error really 'Unknown MYSQL server host ' localhost' <11004>', as in '<space>localhost? Could it be your code is not actually what you pasted, and the is a space before $hostname?

the code is identical, i.e. NO space before 'localhost' tried with 127.0.0.1 get failed: access denied for user 'test_user'@'localhost' I am doing this and still doesn't work

use test;
# create table  (name char(20));
CREATE USER 'test_user'@'localhost';
GRANT ALL PRIVILEGES ON * . * TO 'test_user'@'localhost';
select * from ttt;
[download]

seems like the 'user' does not have access privileges. Any ideas?