Hello David.
We use 4D and the pdo driver in our company and I compiled it up to PHP 7.
I recently decided to publish the code changes (mainly to make it more easy if one of my colleagues gets a new php version - normally I have the most recent one.)
You can access the code here:
I generally skip the make test section. I compiled it on arch linux with PHP 7. So feel free to use it.
If you have comments or suggestions, just use the email address as provided in the repo. I usually do not check my google mails. ;-)
Cheers