why timezone_name_from_abbr fetching wrong result?

Question

I face weird problem on converting offset to timezone name.
I use follwing code to convert offset to timezone.

$timezoneOffset = "+05:30";
echo $timezone_name = timezone_name_from_abbr("",$timezoneOffset*3600,0);

output: Asia/Karachi

Expected output: Asia/Kolkata

To check offset i use

$timezone = 'Asia/Kolkata';
$time = new \DateTime('now', new DateTimeZone($timezone));
$timezoneOffset = $time->format('P');  //output:  +05:30

$timezone_name = timezone_name_from_abbr("",$timezoneOffset*3600,0);
echo $timezone_name;exit;

still the output is Asia/Karachi

So what is the problem? what should i do to solve this problem?

Thanks in advance.

Answer 1

Your calculation of the $gmtOffset parameter (Offset from GMT in seconds) is incorrect.

In PHP, "+05:30" * 3600 gives 18000 as the result. This is because the string is converted to the integer 5 and then multiplied. This of course means that you're calling timezone_name_from_abbr() with an offset of 300 minutes rather than your expected 330 minutes, leading to the "wrong" timezone name being returned.

If you wish to keep your existing $timezoneOffset string, the following can be used to convert to the timezone offset in seconds.

$timezoneOffset = "+05:30";
$offsetSeconds = DateTime::createFromFormat('P', $timezoneOffset)->format('Z');