So the problem changed from what it was, i\'ll leave the original question below to prevent bad reviews on answers like I had after someone editing his question I answered :
Can you try 127.0.0.1
as the server name instead of localhost
?
IIRC, with some mySQL drivers / adapters, this decides whether the socket is used for establishing the connection or not.
Using the connection which works, run the query:
show variables like 'socket';
(this behaves just like a select statement)...and you'll get the path of the running socket.
Then check the file permissions.
One year later, I found a solution for this issue : using a SQLite database. PDO worked fine, but not with MySQL
** EDIT ** as everyone is downvoting this: This solved my issue (I'm the OP). I was using Doctrine, so switching RDBMS was easy and quick. Also the website was some a home made CMS, with very few trafic, so SQLite was fine.
I know it's not a real "Answer" to the problem, but if someone is in the same context: a crappy shared hosting which you can't change with this weird PDO-MySQL bug AND is using doctrine. This IS a solution. I can delete this answer, but if I had thought of this at the time of the OP, I would have saved a lot of time.
Is your server running with SeLinux enabled (enforcing)? If it is, try running as root:
# setsebool -P httpd_can_network_connect on
I found the reason for the strange behaviour. If bind-address is different to 127.0.0.1 or 0.0.0.0 (all addresses) PDO can't connect to 127.0.0.1.
The Issue In the Mysql configuration It you need to disable the option of skip-networking
in my.conf configuration file this should work fine
reference
http://www.wolfcms.org/forum/post7098.html#p7098