How to connect to mssql using pdo through PHP and Linux?

Try

$dbh = new PDO ("mssql:host=$hostname;dbname=$dbname","$username","$pw");

$hostname may need to be configured as either...
$hostname.':'.$port;

OR

$hostname.','.$port;

The PDO mssql driver is no more, use sqlsrv (under php windows) or dblib (under php linux)

http://msdn.microsoft.com/en-us/sqlserver/ff657782.aspx

http://www.php.net/manual/en/ref.pdo-dblib.php

I am running Ubuntu 14.04. Trying to connect to MSSQL I got "Uncaught exception 'PDOException' with message 'could not find driver'". It seems that I was missing the dblib/sybase PHP extension.

I had to run:

sudo apt-get install php5-sybase freetds-common libsybdb5 \ 
&& sudo apache2ctl restart

Works fine now.