Description:
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We have two instances of mysql running, 4.1x on port 3306 using /tmp/mysql.sock and 5.0.18 on port 3307 using /tmp/mysql5.0.18/mysql.sock.

If I connect using the dsn and specify the port, like so:
$db = new PDO('mysql:host=localhost;port=3306;dbname=dbname', 'user', 'pass');

I actually connect to the 5.0.18 instance on 3307.  I know this based on the results of the query executed later.  If, however, I connect using the unix_socket parameter and point it at the 3306 socket file, it seems to work correctly.  Again, I know this because the results of the query are correct.

I wouldn't rule out configuration problems on my end, but even if that were the case it would appear you cannot specify a port to override a configuration value

Reproduce code:
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mysql on 3306 (/tmp/mysql.sock)
select count(*) from users;   //result 5

mysql on 3307 (/tmp/mysql5.0.18/mysql.sock)
select count(*) from users;   //result 2

$db = new PDO('mysql:host=localhost;port=3306;dbname=dbname', 'user', 'pass');
$result = $db->query("select count(*) from users");
print_r($result);

//Array ( [count(*)] => 2 [0] => 2 ) //expecting 5

$db = new PDO('mysql:unix_socket=/tmp/mysql.sock;dbname=dbname', 'user', 'pass');
$result = $db->query("select count(*) from users");
print_r($result);

//Array ( [count(*)] => 5 [0] => 5 )


Expected result:
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I expect unix_socket=/tmp/mysql.sock and port=3306 to produce the same results.

Actual result:
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when specifying a port number as part of the dsn it does not seem to be honored.