Getting the Maxmind GeoIP ISP database wot work with PECL provider

Currently I am using the HTTP-Server-Module for resolving user’s ip address to a geolocation.

However I would like to switch to the recommended PECL-Module to be able to also use non-browser based tracking (e.g. PHP API).

What I like to know about the user is basically only the country and the ISP. The HTTP-Server-Module (using nginx’s FastCGI) performs well but is not working for non-browser based tracking.

So I try to setup the PECL-Module by setting the “geoip.custom_directory” property to “/usr/share/GeoIP” where my databases are located. A directory listing looks as follows:

/usr/share/GeoIP:
total 69M
lrwxrwxrwx 1 root root   46 2016-06-17 10:19 GeoIPASNum.dat -> /var/lib/geoip-database-contrib/GeoIPASNum.dat
lrwxrwxrwx 1 root root   48 2016-06-17 10:19 GeoIPASNumv6.dat -> /var/lib/geoip-database-contrib/GeoIPASNumv6.dat
lrwxrwxrwx 1 root root   31 2018-01-15 10:21 GeoIPCity.dat -> /etc/alternatives/GeoIPCity.dat
lrwxrwxrwx 1 root root   41 2016-06-17 10:19 GeoIP.dat -> /var/lib/geoip-database-contrib/GeoIP.dat
lrwxrwxrwx 1 root root   43 2016-06-17 10:19 GeoIPv6.dat -> /var/lib/geoip-database-contrib/GeoIPv6.dat
-rw-r--r-- 1 root root 5.7M 2018-01-09 17:13 GeoLite2-ASN.mmdb
-rw-r--r-- 1 root root  61M 2018-01-05 16:10 GeoLite2-City.mmdb
-rw-r--r-- 1 root root 3.2M 2018-01-05 15:56 GeoLite2-Country.mmdb
-rwxr--r-- 1 root root 1.1K 2018-01-16 09:28 GeoLite2-update.sh
lrwxrwxrwx 1 root root   47 2016-06-17 10:19 GeoLiteCity.dat -> /var/lib/geoip-database-contrib/GeoLiteCity.dat
lrwxrwxrwx 1 root root   49 2016-06-17 10:19 GeoLiteCityv6.dat -> /var/lib/geoip-database-contrib/GeoLiteCityv6.dat

However, Piwik/GeoIP seems to only detect “City, Country”.

How to setup Piwik/Matomo’s GeoIP-PECL-Module to work also with ISP (ASNNum) database?