Timezone select

system/Helpers/date_helper.php

@@ -69,3 +69,34 @@ function now(string $timezone = null): int
 		return mktime($hour, $minute, $second, $month, $day, $year);
 	}
 }
+
+if (! function_exists('timezone_select'))
+{
+	/**
+	 * Generates a select field of all available timezones
+	 *
+	 * Returns a string with the formatted HTML
+	 *
+	 * @param string $class    Optional class to apply to the select field
+	 * @param string $default  Default value for initial selection
+	 * @param int    $what     One of the DateTimeZone class constants (for listIdentifiers)
+	 * @param string $country  A two-letter ISO 3166-1 compatible country code (for listIdentifiers)
+	 *
+	 * @return string
+	 * @throws \Exception
+	 */
+	function timezone_select(string $class = '', string $default = '', int $what = \DateTimeZone::ALL, string $country = null): string
+	{
+		$timezones = \DateTimeZone::listIdentifiers($what, $country);
+
+		$buffer = "<select name='timezone' class='{$class}'>" . PHP_EOL;
+		foreach ($timezones as $timezone)
+		{
+			$selected = ($timezone == $default) ? 'selected' : '';
+			$buffer .= "<option value='{$timezone}' {$selected}>{$timezone}</option>" . PHP_EOL;
+		}
+		$buffer .= "</select>" . PHP_EOL;
+
+		return $buffer;
+	}
+}

user_guide_src/source/helpers/date_helper.rst

@@ -43,5 +43,21 @@ The following functions are available:
 	If a timezone is not provided, it will return ``time()`` based on the
 	**time_reference** setting.
 
+.. php:function:: timezone_select([$class = '', $default = '', $what = \DateTimeZone::ALL, $country = null])
+
+	:param	string	$class: Optional class to apply to the select field
+	:param	string	$default: Default value for initial selection
+	:param	int	$what: DateTimeZone class constants (see `listIdentifiers <https://www.php.net/manual/en/datetimezone.listidentifiers.php>`_)
+	:param	string	$country: A two-letter ISO 3166-1 compatible country code (see `listIdentifiers <https://www.php.net/manual/en/datetimezone.listidentifiers.php>`_)
+	:returns:	Preformatted HTML select field
+	:rtype:	string
+
+	Generates a `select` form field of available timezones (optionally filtered by `$what` and `$country`).
+	You can supply an option class to apply to the field to make formatting easier, as well as a default
+	selected value.
+	::
+
+		echo timezone_select('custom-select', 'America/New_York');
+
 Many functions previously found in the CodeIgniter 3 ``date_helper`` have been moved to the ``I18n``
 module in CodeIgniter 4.