Initial Installation Error

Hi David.
I am getting an error during the initial setup. When I try to run the install, the log shows.

[Error Code: 1] Uncaught Error: Call to undefined function mysqli_connect() in /home/pi/www/grav/sites/journal/control/classes/class.db.php:20
Stack trace:
#0 /home/pi/www/grav/sites/journal/install/index.php(44): db->db_conn()
#1 {main}
  thrown
[Date/Time: 18 March 2017 @ 14:08PM]
[Fatal error on line 20 in file /home/pi/www/grav/sites/journal/control/classes/class.db.php]

I have tried uncommenting extensions in php.ini
php_mysqli.dll
php_pdo_mysql.dll

I am running:
Ngnix
php7

Is php7 not supported?