PHP Startup : Unable to load dynamic library PGSQL

I had a very similar issue:

I fixed it by applying the same patch as for this subject: pdo_parse_params error in pdo_odbc.so whenever PHP starts in Fedora 20

In a nutshell: if a module has already been loaded by the /etc/php/7.2/mods-available/<module>.ini (or equivalent path for your OS), then the module should not be uncommented (= made active) in the php.ini files. (two of them, cli and server).

You may ensure this, by checking phpinfo(), and observe how pdo_pgsql is still active in there, despite the line being commented in php.ini!

You must properly install the PostgreSQL module and enable it. http://php.net/manual/en/pgsql.installation.php

P.S. do not use '.dll' files on the servers with UNIX based OS, because these extensions are compiled for the Windows operating system (for UNIX based OS you must use '.so' files).