Improve internal timezone handling

common/framework/datetime.php

@@ -0,0 +1,101 @@
+<?php
+
+namespace Rhymix\Framework;
+
+/**
+ * The datetime class.
+ */
+class DateTime
+{
+	/**
+	 * Time zone objects and settings are cached here.
+	 */
+	protected static $_timezones = array();
+	
+	/**
+	 * Get the timezone to display for the current user.
+	 * 
+	 * @return string
+	 */
+	public static function getCurrentUserTimezone()
+	{
+		if (isset($_SESSION['timezone']))
+		{
+			return $_SESSION['timezone'];
+		}
+		else
+		{
+			return Config::get('locale.default_timezone');
+		}
+	}
+	
+	/**
+	 * Get the list of time zones supported on this server.
+	 * 
+	 * @return array
+	 */
+	public static function getTimezoneList()
+	{
+		$result = array();
+		$tzlist = \DateTimeZone::listIdentifiers();
+		foreach ($tzlist as $tzid)
+		{
+			if (!preg_match('/^(?:A|Europe|Indian|Pacific)/', $tzid)) continue;
+			$name = str_replace('_', ' ', $tzid);
+			$datetime = new \DateTime(null, new \DateTimeZone($tzid));
+			$offset = $datetime->getOffset();
+			$offset = ($offset >= 0 ? '+' : '-') . sprintf('%02d', floor(abs($offset) / 3600)) . ':' . sprintf('%02d', (abs($offset) % 3600) / 60);
+			unset($datetime);
+			$result[$tzid] = "$name ($offset)";
+		}
+		asort($result);
+		$result['Etc/UTC'] = 'GMT/UTC (+00:00)';
+		return $result;
+	}
+	
+	/**
+	 * Get the absolute (UTC) offset of a timezone.
+	 * 
+	 * @param string $timezone Timezone identifier, e.g. Asia/Seoul
+	 * @param int $timestamp Unix timestamp (optional, default is now)
+	 * @return int
+	 */
+	public static function getTimezoneOffset($timezone, $timestamp = null)
+	{
+		if (!isset(self::$_timezones[$timezone]))
+		{
+			self::$_timezones[$timezone] = new \DateTimeZone($timezone);
+		}
+		$datetime = new \DateTime();
+		$datetime->setTimestamp($timestamp ?: time());
+		$datetime->setTimezone(self::$_timezones[$timezone]);
+		return $datetime->getOffset();
+	}
+	
+	/**
+	 * Get the relative offset between a timezone and Rhymix's internal timezone.
+	 * 
+	 * @param string $timezone Timezone identifier, e.g. Asia/Seoul
+	 * @param int $timestamp Unix timestamp (optional, default is now)
+	 * @return int
+	 */
+	public static function getTimezoneOffsetFromInternal($timezone, $timestamp = null)
+	{
+		return self::getTimezoneOffset($timezone, $timestamp) - Config::get('locale.internal_timezone');
+	}
+	
+	/**
+	 * Get a PHP time zone by UTC offset.
+	 * 
+	 * @param int $offset
+	 * @return bool
+	 */
+	public static function getTimezoneNameByOffset($offset)
+	{
+		switch ($offset)
+		{
+			case 0: return 'Etc/UTC';
+			default: return 'Etc/GMT' . ($offset > 0 ? '-' : '+') . intval(abs($offset / 3600));
+		}
+	}
+}