Author of GRB, PICC and URBIS to OSM migration toolkit
I professionally occupy myself in studying the GRB dataset, PICC and URBIS datasets on accuracy and usuability. One of the specialisations is to combine, merge and enhance external datasets with OpenStreetMap data and the other way around. I subsequently created a web based toolkit to assist OSM mappers to merge, verify and input data from GRB (Grootschalig Referentie Bestand) with OpenStreetMaps , PICC and Urbis into OSM.
PHP Reverse geocoding library
I've created a PHP abstraction library to perform geocoding from all the known engines. See php-georev-class repository. It work(ed) with all major public services but it was designed to work very well with nominatim geocoder. It's a bit aged as it was written before composer became popular but untill this day it is still being used by customers in combination with our inhouse hosted customized and data enhanced nominatim geocoding service.
reverse geocoding library