<?php
ini_set('date.timezone', 'UTC');
$cal1 = IntlCalendar::createInstance(NULL, 'es_ES');
var_dump($cal1->getFirstDayOfWeek()); // Monday
$cal1->set(2013, 1 /* February */, 3); // a Sunday
var_dump($cal1->get(IntlCalendar::FIELD_WEEK_OF_YEAR)); // 5
$cal2 = IntlCalendar::createInstance(NULL, 'en_US');
var_dump($cal2->getFirstDayOfWeek()); // Sunday
$cal2->set(2013, 1 /* February */, 3); // a Sunday
var_dump($cal2->get(IntlCalendar::FIELD_WEEK_OF_YEAR)); // 6
The above example will output:
int(2)
int(5)
int(1)
int(6)