Generating a drop down list of timezones with PHP

Following user210179's example above, I've written the following function to generate me a list of all timezones with their offsets:

function generate_timezone_list()
{
    static $regions = array(
        DateTimeZone::AFRICA,
        DateTimeZone::AMERICA,
        DateTimeZone::ANTARCTICA,
        DateTimeZone::ASIA,
        DateTimeZone::ATLANTIC,
        DateTimeZone::AUSTRALIA,
        DateTimeZone::EUROPE,
        DateTimeZone::INDIAN,
        DateTimeZone::PACIFIC,
    );

    $timezones = array();
    foreach( $regions as $region )
    {
        $timezones = array_merge( $timezones, DateTimeZone::listIdentifiers( $region ) );
    }

    $timezone_offsets = array();
    foreach( $timezones as $timezone )
    {
        $tz = new DateTimeZone($timezone);
        $timezone_offsets[$timezone] = $tz->getOffset(new DateTime);
    }

    // sort timezone by offset
    asort($timezone_offsets);

    $timezone_list = array();
    foreach( $timezone_offsets as $timezone => $offset )
    {
        $offset_prefix = $offset < 0 ? '-' : '+';
        $offset_formatted = gmdate( 'H:i', abs($offset) );

        $pretty_offset = "UTC${offset_prefix}${offset_formatted}";

        $timezone_list[$timezone] = "(${pretty_offset}) $timezone";
    }

    return $timezone_list;
}

This will generate an array looking like:

[Pacific/Midway] => (UTC-11:00) Pacific/Midway
[Pacific/Pago_Pago] => (UTC-11:00) Pacific/Pago_Pago
[Pacific/Niue] => (UTC-11:00) Pacific/Niue
[Pacific/Honolulu] => (UTC-10:00) Pacific/Honolulu
[Pacific/Fakaofo] => (UTC-10:00) Pacific/Fakaofo
…

It's currently sorted by offsets, but you can easily sort by the timezone name by doing a ksort() instead of asort().

I would do it in PHP, except I would avoid doing preg_match 100 some times and do this to generate your list.

$tzlist = DateTimeZone::listIdentifiers(DateTimeZone::ALL);

Also, I would use PHP's names for the 'timezones' and forget about GMT offsets, which will change based on DST. Code like that in phpbb is only that way b/c they are still supporting PHP4 and can't rely on the DateTime or DateTimeZone objects being there.