pdo sqlite could not find driver... php file not processing

You need

[PDO_SQLITE]
extension=pdo_sqlite.so

to be enabled, for sqlite:.subscribers.db

or, for windows:

[PHP_PDO_SQLITE]
extension=php_pdo_sqlite.dll

And ofcourse this extension in your ext directory

I had to actually install the extension, and this is how i did on Ubuntu 16 running PHP 7.1:

sudo apt install php7.1-sqlite3