1. Install the necessary RPM's for PostgreSQL. Currently, we recommend version 8.4;

CentOS 5.x;
yum install -y postgresql84*
service postgresql initdb

?CentOS 6.x;
/scripts/installpostgres

2. Login to WHM and complete the configuration;
    1. Navigate to WHM -> SQL Services -> PostgreSQL
    2. Click on Install Config
    3. Come back to the PostgreSQL page and click Install Users
    4. Come back to the PostgreSQL page and choose a root password.

3. Rebuild Apache with PostgreSQL support (listed in the Exhaustive PHP Options page in EasyApache)

4. Optionally, you can add the PDO module for PostgreSQL with the following command;
 pecl install pdo_pgsql

Enable pdo_pgsql (postgres PDO driver) in cpanel server
You can install pdo_pgsql via two methods

1. Via pecl

pecl install pdo_pgsql

If this fails, enable it via manual compilation below

2. Manual compilation

Download the PDO driver from the PECL website below.

http://pecl.php.net/package/PDO_PGSQL

Download it and enter the downloaded directory by

wget http://pecl.php.net/get/PDO_PGSQL-1.0.2.tgz
tar -xzf PDO_PGSQL-1.0.2.tgz
cd PDO-PSQL-1.0.2/

Once this is done, run the standard commands for building a PHP extension.

phpize
./configure
make
make install

Once this is done, you can add the extension to php.ini.

cd /usr/local/lib/
vim php.ini
extension=pdo_pgsql.so

Finally, restart Apache

service httpd restart

Verify it via commandline

php -i | grep pdo_pgsql

Referencia: