$ /opt/php5/bin/phpize
$ ./configure --with-php-config=/opt/php5/bin/php-config --with-icu-dir=/opt/icu
$ make
If your ICU is installed to a non-standard directory then you might want to
specify its location in
LD_LIBRARY_PATH
environment variable so that dynamic linker can find it:
$ export LD_LIBRARY_PATH=/opt/icu/lib
Otherwise, if PHP and ICU are installed to their default locations, then the
additional options to `configure' are not needed.