How to check is timezone identifier valid from code?

Question

I\'ll try to explain what\'s the problem here.

According to list of supported timezones from PHP manual, I can see all valid TZ identifiers in PHP.

My first

Answer 1

Just an addendum to Cal's excellent answer. I think the following might be even faster...

function isValidTimezoneID($tzid) {
    if (empty($tzid)) {
        return false;
    }
    foreach (timezone_abbreviations_list() as $zone) {
        foreach ($zone as $item) {
            if ($item["timezone_id"] == $tzid) {
                return true;
            }
        }
    }
    return false;
}