Homestead - L4.2 - PGSQL - PDOException - could not find driver

Hi all, hopefully somebody can help.

I have a new installation of homestead with a laravel 4.2 application making use of postgresql.

The error in the log file when trying to interact with the db is: local.ERROR: exception 'PDOException' with message 'could not find driver' in :

I have tested the following:

1. According to a phpinfo(); page php is configured with pdo + pdo_pgsql
2. Verified no 1 with the following code:

<?php

foreach (PDO::getAvailableDrivers() as $driver)
    {
        echo $driver . '<br />';
    }

$dbh = new PDO ('pgsql:host=xxxx;dbname=xxxx', 'xxxx', 'xxxx')
or die ("Error");

try {
    $dbh = new PDO('pgsql:host=xxxx;dbname=xxxx', 'xxxx', 'xxxx');
    foreach($dbh->query('SELECT * from users') as $row) {
        print_r($row);
    }
    $dbh = null;
} catch (PDOException $e) {
    print "Error!: " . $e->getMessage() . "<br/>";
    die();
}

which produced the following output:

mysql
pgsql
sqlite
Array ( [id] => 1 .........................................

3. I can run php artisan migrate and php artisan tinker and create the db tables and create db entries.

Thus I have determined the following:

1. PHP is running and configured correctly via both web and cli
2. Postgresql is running and accessible via artisan
3. I don't know why the laravel web interaction with pgsql is not working

I am at my wits end and would appreciate any help.