class.ilTimeZone.php

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<?php
/*
        +-----------------------------------------------------------------------------+
        | ILIAS open source                                                           |
        +-----------------------------------------------------------------------------+
        | Copyright (c) 1998-2006 ILIAS open source, University of Cologne            |
        |                                                                             |
        | This program is free software; you can redistribute it and/or               |
        | modify it under the terms of the GNU General Public License                 |
        | as published by the Free Software Foundation; either version 2              |
        | of the License, or (at your option) any later version.                      |
        |                                                                             |
        | This program is distributed in the hope that it will be useful,             |
        | but WITHOUT ANY WARRANTY; without even the implied warranty of              |
        | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               |
        | GNU General Public License for more details.                                |
        |                                                                             |
        | You should have received a copy of the GNU General Public License           |
        | along with this program; if not, write to the Free Software                 |
        | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. |
        +-----------------------------------------------------------------------------+
*/

include_once('Services/Calendar/classes/class.ilTimeZoneException.php');

class ilTimeZone
{
        const UTC = 'UTC';
        
        public static $instances = array();
        public static $valid_tz = array();

        protected static $default_timezone = '';
        protected static $current_timezone = '';
        protected static $server_timezone = '';
        
        protected $log;
        protected $timezone = "UTC";

        private function __construct($a_timezone)
        {
                global $ilLog;

                $this->log = $ilLog;

                if($a_timezone)
                {
                        $this->timezone = $a_timezone;
                }
                else
                {
                        $this->timezone = self::_getDefaultTimeZone();
                }
                
                if(!self::$server_timezone)
                {
                        self::$server_timezone = self::_getDefaultTimeZone();
                }
                
                if(!self::$default_timezone)
                {
                        self::_getDefaultTimeZone();
                }
        }
        
        public function getIdentifier()
        {
                return $this->timezone;
        }
        
        public static function _getInstance($a_tz = '')
        {
                global $ilLog;
                
                if(!$a_tz)
                {
                        $a_tz = self::_getDefaultTimeZone();
                }
                
                if(isset(self::$instances[$a_tz]))
                {
                        $instance = self::$instances[$a_tz];
                }
                else
                {
                        $instance = self::$instances[$a_tz] = new ilTimeZone($a_tz);
                }

                // Validate timezone if it is not validated before
                if(!array_key_exists($instance->getIdentifier(),self::$valid_tz))
                {
                        if(!$instance->validateTZ())
                        {
                                throw new ilTimeZoneException('Unsupported timezone given.');
                        }
                        self::$valid_tz[$instance->getIdentifier()] = true;
                }

                // now validate timezone setting
                return $instance;
        }
        
        public function switchTZ()
        {
                try
                {
                        self::_switchTimeZone($this->timezone);
                        return true;
                }
                catch(ilTimeZoneException $exc)
                {
                        // Shouldn't happen since this has been checked during initialisation
                        $this->log->write(__METHOD__.': Unsupported timezone given: Timzone: '.$this->timezone);
                        return false;
                }
        }
        
        public function restoreTZ()
        {
                try
                {
                        self::_switchTimeZone(self::$default_timezone);
                        return true;
                }
                catch(ilTimeZoneException $e)
                 {
                        // Shouldn't happen since this has been checked during initialisation
                        $this->log->write(__METHOD__.': Unsupported timezone given: Timzone: '.$this->timezone);
                        return false;
                 }
        }
        
        public function validateTZ()
        {
                // this is done by switching to the current tz
                if($this->switchTZ() and $this->restoreTZ())
                {
                        return true;
                }
                return false;
        }
        
        protected static function _switchTimeZone($a_timezone)
        {
                global $ilLog;
                
                if(self::$current_timezone == $a_timezone)
                {
                        #$ilLog->write(__METHOD__.': Do not switch to active timezone: '.$a_timezone);
                        return true;
                }
                
                // PHP >= 5.2.0
                if(function_exists('date_default_timezone_set'))
                {
                        if(!date_default_timezone_set($a_timezone))
                        {
                                $ilLog->write(__METHOD__.': Invalid timezone given. Timezone: '.$a_timezone);
                                throw new ilTimeZoneException('Invalid timezone given'); 
                        }
                        #$ilLog->write(__METHOD__.': Switched timezone to: '.$a_timezone);
                        self::$current_timezone = $a_timezone;
                        return true;
                }
                if(!putenv('TZ='.$a_timezone))
                {
                        $ilLog->write(__METHOD__.': Cannot set TZ environment variable. Please register TZ in php.ini (safe_mode_allowed_env_vars). Timezone');
                        throw new ilTimeZoneException('Cannot set TZ environment variable.'); 
                }
                self::$current_timezone = $a_timezone;
                return true;
        }
        
        public static function _setDefaultTimeZone($a_tz)
        {
                // Save the server timezone, since there is no way to read later.
                if(!self::$server_timezone)
                {
                        self::$server_timezone = self::_getDefaultTimeZone();
                }
                
                self::$default_timezone = $a_tz;
        }
        
        public static function _restoreDefaultTimeZone()
        {
                self::$default_timezone = self::$server_timezone;
                self::_switchTimeZone(self::$default_timezone);
        }
        
        public static function _getDefaultTimeZone()
        {
                if(strlen(self::$default_timezone))
                {
                        return self::$default_timezone;
                }
                // PHP >= 5.2.0
                if(function_exists('date_default_timezone_get') and $tz = date_default_timezone_get())
                {
                        return self::$default_timezone = $tz;
                }
                // PHP ini option (PHP >= 5.1.0)
                if($tz = ini_get('date.timezone'))
                {
                        return self::$default_timezone = $tz;
                }
                // is $_ENV['PHP_TZ'] set ?
                if($tz = getenv('PHP_TZ'))
                {
                        return self::$default_timezone = $tz;
                }
                // is $_ENV['TZ'] set ?
                if($tz = getenv('TZ'))
                {
                        return self::$default_timezone = $tz;
                }
                if(strlen($tz = date('T')))
                {
                        return self::$default_timezone = $tz;
                }
                return self::$default_timezone = self::UTC;
        }
}
?>