Installing Drupal with Postgresql

I'm trying to install Drupal using Postgresql as the backend database and have read that I need something called php5-pdo_pgsql to be able to configure Drupal to use Postgresql.

It is mentioned here:-

but is not available as an installable PKG. Can I tell if Postgresql on FreeBSD is built with this option?

And does anyone know of any guides for setting up Drupal/Postgresql/FreeBSD?
Actually after looking again at Drupal, it looks as though using with Postgresql is supported out of the box with Drupal 8 and includes a INSTALL.pgsql.txt for installing with Postgresql.

Unfortunately my install falls at the first hurdle in Install.php with

[:error] [pid xxxxxx] [client xxxxxxx] PHP fatal error: Call to undefined function Symfony//Component//Yaml//ctype_digit() in ****

/usr/local/www/apache24/data/drupal/vendor/symfony/yaml/Inline.php on line 504

that line contains:

case ctype_digit($scalar):

**** the line marked with **** should have backslashes rather than forward slashes

I'm using FreeBSD 10.3-RELEASE with Xfce and the backslash key prints a '<'. No idea why...
It seems that I am missing PDO support for POSTGRESQL in PHP.

How do I add it? Is there a PKG I need to install?
After getting Drupal 8 working with Postgresql six months ago it stopped working and now I'm trying to get it working again, but have the same problems in not seeing Postgresql as a database option for Drupal. This time I'm trying to use Postgresql 9.6 but when attempting to install php56-pdo_pgsql, postgresql93_client is a dependency so postgresql96_client will most likely be removed.

Is there any way to remove this dependency? If I try to build from source will there be also an attempt to make this backlevel version of the client?