$ sudo apt-get update
$ sudo apt-get install php-mdb2-driver-pgsql 

php-mdb2-driver-pgsql is installed in your system.

Make ensure the php-mdb2-driver-pgsql package were installed using the commands given below,

$ sudo dpkg-query -l | grep php-mdb2-driver-pgsql *

You will get with php-mdb2-driver-pgsql package name, version, architecture and description in a table

php-mdb2-driver-pgsql package basic information: