Time zone abbreviation.
Offset from GMT in seconds. Defaults to -1 which means that first found time zone corresponding to abbr is returned. Otherwise exact offset is searched and only if not found then the first time zone with any offset is returned.
Daylight saving time indicator. If abbr doesn't exist then the time zone is searched solely by offset and isdst.
echo timezone_name_from_abbr("CET") . "\n";
echo timezone_name_from_abbr("", 3600, 0) . "\n";
The above example will output something similar to: