class.ilTimeZone.php

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<?php

declare(strict_types=1);
class ilTimeZone
{
    public const UTC = 'UTC';

    public static array $instances = array();
    public static array $valid_tz = array();

    protected static string $default_timezone = '';
    protected static string $current_timezone = '';
    protected static string $server_timezone = '';

    protected ilLogger $log;
    protected string $timezone = "UTC";

    private function __construct(string $a_timezone)
    {
        global $DIC;

        $this->log = $DIC->logger()->cal();

        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 __sleep()
    {
        return array('timezone');
    }

    public function __wakeup()
    {
        global $DIC;
        $this->log = $DIC->logger()->cal();
    }

    public function getIdentifier(): string
    {
        return $this->timezone;
    }

    public static function _getInstance(string $a_tz = ''): ilTimeZone
    {
        if (!$a_tz) {
            $a_tz = self::_getDefaultTimeZone();
        }

        $instance = self::$instances[$a_tz] ?? (self::$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(): bool
    {
        try {
            self::_switchTimeZone($this->timezone);
            return true;
        } catch (ilTimeZoneException $exc) {
            // Shouldn't happen since this has been checked during initialisation
            $this->log->warning(': Unsupported timezone given: Timzone: ' . $this->timezone);
            return false;
        }
    }

    public function restoreTZ(): bool
    {
        try {
            self::_switchTimeZone(self::$default_timezone);
            return true;
        } catch (ilTimeZoneException $e) {
            // Shouldn't happen since this has been checked during initialisation
            $this->log->warning(': Unsupported timezone given: Timzone: ' . $this->timezone);
            return false;
        }
    }

    public function validateTZ(): bool
    {
        // this is done by switching to the current tz
        if ($this->switchTZ() and $this->restoreTZ()) {
            return true;
        }
        return false;
    }

    protected static function _switchTimeZone(string $a_timezone): bool
    {
        global $DIC;

        $logger = $DIC->logger()->cal();
        if (self::$current_timezone == $a_timezone) {
            return true;
        }

        // PHP >= 5.2.0
        if (function_exists('date_default_timezone_set')) {
            if (!date_default_timezone_set($a_timezone)) {
                $logger->info('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)) {
            $logger->warning('Cannot set TZ environment variable. Please register TZ in php.ini (safe_mode_allowed_env_vars). Timezone');
            throw new ilTimeZoneException('Cannot set TZ environment variable.');
        }
        self::$current_timezone = $a_timezone;
        return true;
    }

    public static function _setDefaultTimeZone(string $a_tz): void
    {
        // Save the server timezone, since there is no way to read later.
        if (!self::$server_timezone) {
            self::$server_timezone = self::_getDefaultTimeZone();
        }
        self::$default_timezone = $a_tz;
    }

    public static function _restoreDefaultTimeZone(): void
    {
        self::$default_timezone = self::$server_timezone;
        self::_switchTimeZone(self::$default_timezone);
    }

    public static function _getDefaultTimeZone(): string
    {
        if (strlen(self::$default_timezone)) {
            return self::$default_timezone;
        }
        // PHP >= 5.2.0
        // php throws a warning date_default_timezone_get relies on os determination. There is no way to check if this could happen.
        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;
    }

    public static function initDefaultTimeZone(ilIniFile $ini): string
    {
        $tz = $ini->readVariable('server', 'timezone');
        if (!strlen($tz)) {
            $tz = self::_getDefaultTimeZone();
        }
        if (!strlen($tz)) {
            $tz = 'UTC';
        }
        date_default_timezone_set($tz);
        return $tz;
    }
}