Generating a Drop Down List of Timezones with PHP

Most websites need a way to display dates in a user's preferred timezone. Below are two lists of timezones that can be used, as well as one method using the built-in PHP DateTime class that is available in PHP 5 and later.

Using Hardcoded Timezone Lists

This method involves manually creating lists of timezones, either as values in HTML elements or as keys in an array. The example list below shows timezone values that include both the timezone offset and the city name:

(GMT - 12) Baker Island Time
(GMT - 11) Niue Time, Samoa Standard Time

This method is simple and can be used without any additional libraries or code. However, it can be time-consuming to maintain the list as new timezones are added or removed. Also, knowing which timezones are relevant to the user’s country can be difficult.

Using PHP Date and Time Functions

PHP provides several functions and objects that can be used to manage timezones. The DateTimeZone class allows you to create a timezone object and access its offset from UTC. The DateTime class allows you to create a date object and set its timezone. Using these classes, you can generate a drop-down list of timezones dynamically.

$timezones = DateTimeZone::listAbbreviations();

foreach ($timezones as $tz) {
  $name = $tz['timezone_id'];
  $offset = $tz['offset'];

  echo "$name (UTC $offset)";
}

This method is more flexible than using hardcoded lists. It can retrieve the current list of timezones from the PHP installation and automatically adjust for changes in daylight saving time. However, it requires more code to implement and may not be as well-supported on older versions of PHP.

Which Method is Best?

The best method for generating a drop-down list of timezones depends on the specific requirements of the application. If the list of timezones is small and unlikely to change, then using hardcoded values may be sufficient. If the list is large or dynamic, then using the DateTimeZone class or DateTime class may be a better choice.