The GeoNames database contains over 8,000,000 geographical names corresponding to over 6,500,000 unique features. All features are categorized into one out of nine feature classes and further subcategorized into one out of 645 feature codes. Beyond names of places in various languages, data stored include latitude, longitude, elevation, population, administrative subdivision and postal codes. All coordinates use the WGS84 system (World Geodetic System 1984).
Those data are accessible free of charge through a number of Web services and a daily database export. The Web services include direct and reverse geocoding, finding places through postal codes, finding places next to a given place, and finding Wikipedia articles about neighbouring places.
To install the package with pear just do:
$ pear install -f Services_GeoNames
$ pear uninstall Services_GeoNames