system/Session/Handlers/FileHandler.php
public function gc($maxlifetime): bool
	{
		if (! is_dir($this->savePath) || ($directory = opendir($this->savePath)) === false)
		{
			$this->logger->debug("Session: Garbage collector couldn't list files under directory '" . $this->savePath . "'.");

			return false;
		}

		$ts = time() - $maxlifetime;

		$pattern = $this->matchIP === true
			? '[0-9a-f]{32}'
			: '';

		$pattern = sprintf(
			'#\A%s' . $pattern . $this->sessionIDRegex . '\z#',
			preg_quote($this->cookieName)
		);

		while (($file = readdir($directory)) !== false)
		{
			// If the filename doesn't match this pattern, it's either not a session file or is not ours
			if (! preg_match($pattern, $file)
				|| ! is_file($this->savePath . DIRECTORY_SEPARATOR . $file)
				|| ($mtime = filemtime($this->savePath . DIRECTORY_SEPARATOR . $file)) === false
				|| $mtime > $ts
			)
			{
				continue;
			}

			unlink($this->savePath . DIRECTORY_SEPARATOR . $file);
		}

		closedir($directory);

		return true;
	}
public function gc($maxlifetime): bool
	{
		if (! is_dir($this->savePath) || ($directory = opendir($this->savePath)) === false)
		{
			$this->logger->debug("Session: Garbage collector couldn't list files under directory '" . $this->savePath . "'.");

			return false;
		}

		$ts = time() - $maxlifetime;

		$pattern = $this->matchIP === true
			? '[0-9a-f]{32}'
			: '';

		$pattern = sprintf(
			'#\A%s' . $pattern . $this->sessionIDRegex . '\z#',
			preg_quote($this->cookieName)
		);

		while (($file = readdir($directory)) !== false)
		{
			// If the filename doesn't match this pattern, it's either not a session file or is not ours
			if (! preg_match($pattern, $file)
				|| ! is_file($this->savePath . DIRECTORY_SEPARATOR . $file)
				|| ($mtime = filemtime($this->savePath . DIRECTORY_SEPARATOR . $file)) === false
				|| $mtime > $ts
			)
			{
				continue;
			}

			unlink($this->savePath . DIRECTORY_SEPARATOR . $file);
		}

		closedir($directory);

		return true;
	}
Garbage Collector

Deletes expired sessions

@param integer $maxlifetime Maximum lifetime of sessions

@return boolean