timezone_open($timezone)

<?php
   tz = "Indian/mahe";res = timezone_open(tz);     print_r(res);
?>

DateTimeZone Object
(
  [timezone_type] => 3
  [timezone] => Indian/mahe
)

$dateSrc = '2017-06-25 1:50 GMT';
$dateTime = date_create( $dateSrc);

$DateTimeZone = timezone_open ( 'America/Chicago' );
date_timezone_set( $dateTime, $DateTimeZone );
$NewDateTimeZone = date_timezone_get($dateTime);

echo 'New timeZone is '. timezone_name_get($NewDateTimeZone);
echo "\n";

# Using second function.
$dateTime = new DateTime($dateSrc);

$DateTimeZone = new DateTimeZone( 'America/Chicago' );
$dateTime->setTimezone( $DateTimeZone );
$NewDateTimeZone = $dateTime->getTimezone ();

echo 'New timeZone is '. timezone_name_get ($NewDateTimeZone);

New timeZone is America/Chicago
New timeZone is America/Chicago