<?php
$cal = IntlCalendar::createInstance('UTC', 'en_US');
var_dump($cal->getErrorMessage());
$cal->getWeekendTransition(IntlCalendar::DOW_WEDNESDAY);
var_dump($cal->getErrorMessage());
string(12) "U_ZERO_ERROR"
string(82) "intlcal_get_weekend_transition: Error calling ICU method: U_ILLEGAL_ARGUMENT_ERROR"