Internationalization extension (further is referred as Intl) is a wrapper for
ICU library, enabling PHP programmers to perform UCA-conformant collation and
date/time/number/currency formatting in their scripts.
It tends to closely follow ICU APIs, so that people having experience working
with ICU in either C/C++ or Java could easily use the PHP API. Also, this way
ICU documentation would be useful to understand various ICU functions.