Check if timezone has DST

Question

at the moment I am trying to detect if a timezone has DST at all and not if DST affects the timezone at the moment.

My code looks like this at the moment:

function timezoneDoesDST($tzId) {
    $tz = new DateTimeZone($tzId);
    return count($tz->getTransitions(time())) > 0;
}
$tz = new DateTimeZone('UTC');
$termin = new DateTime('2017-08-04 12:00:00',$tz);
$mytimezone=array();
foreach(timezone_abbreviations_list() as $abbr => $timezone){
    foreach($timezone as $val){
        if(isset($val['timezone_id'])){
            $found = 0;
            $tz2 = new DateTimeZone($val['timezone_id']);
            $termin->setTimezone($tz2);
            foreach($mytimezone as $mytz)
            {
                if($mytz['time'] == $termin->format('Y-m-d H:i:s'))
                {
                    $found = 1;
                    if(timezoneDoesDST($val['timezone_id']))
                    {
                        $found = 0;
                    }
                }
            }
            if($found == 0)
            {
                $mytimezone[] = array('time' => $termin->format('Y-m-d H:i:s'),'timezone_id' => $val['timezone_id']);
            }
        }
    }
}
foreach($mytimezone as $mytz)
{
    echo $mytz['time'].' - '.$mytz['timezone_id'].'<br />';
}

The thing is, I won't to display all different timezones with a different time and timezones which has a DST at all.

But at the moment it displays me all timezones and if I remove this:

if(timezoneDoesDST($val['timezone_id']))
{
    $found = 0;
}

It just displays me timezones with different time

Thanks

Answer 1

Ok I have updated my code a bit to reduce the amount of selected timezones if anybody needs this:

    function timezoneDoesDST($tzId) {
        $tz = new DateTimeZone($tzId);
        return count($tz->getTransitions(time())) > 0;
    }
    $tz = new DateTimeZone('UTC');
    $termin = new DateTime('2017-08-04 12:00:00',$tz);
    $mytimezone=array();
    $y = 0;
    foreach(timezone_abbreviations_list() as $abbr => $timezone){

        foreach($timezone as $val){
            if(isset($val['timezone_id'])){
                $y++;
                $found = 0;
                $found2 = 0;
                $tz2 = new DateTimeZone($val['timezone_id']);
                $termin->setTimezone($tz2);
                foreach($mytimezone as $mytz)
                {
                    if($mytz['time'] == $termin->format('Y-m-d H:i:s'))
                    {
                        $found = 1;
                    }
                    if(timezoneDoesDST($val['timezone_id']))
                    {
                        if($mytz['time'] == $termin->format('Y-m-d H:i:s') and $mytz['timezone_id'] != $val['timezone_id'] and $mytz['DST'] == 0)
                        {
                            $found2 = 1;
                            $found = 0;
                        }
                    }
                }
                if($found == 0)
                {
                    $mytimezone[] = array('time' => $termin->format('Y-m-d H:i:s'),'timezone_id' => $val['timezone_id'],'DST' => $found2);
                }
            }
        }
    }
    $mylist = count($mytimezone);
    echo $mylist.' - '.$y.'<br /><br />';
    foreach($mytimezone as $mytz)
    {
        echo $mytz['time'].' - '.$mytz['DST'].' - '.$mytz['timezone_id'].'<br />';
    }

This reduces it from about 1500 to 68 different timezones with and without DST.

Cheers and thanks to all.