How to build with actual ICU version (tested on debian 8.2):
wget http://download.icu-project.org/files/icu4c/56.1/icu4c-56_1-src.tgz tar xvzf icu4c-56_1-src.tgz cd icu/source ./configure --prefix=/opt/icu4c-php && make && make install
Add to php build config --with-icu-dir=/opt/icu4c-php
Build extension only:
make pull && checkout actual verion branch in php-src dir
cd ~/php-7-debian/php-src/ext/intl phpize7.0 ./configure --with-php-config=/usr/bin/php-config7.0 --with-icu-dir=/opt/icu4c-php make (sudo) make install
Create 20-intl.ini config files (if needed) in:
/etc/php/7.0/cli/conf.d
/etc/php/7.0/fpm/conf.d
; configuration for php intl module
; priority=20
extension=intl.so
Restart (reload) php.