system/Session/Session.php
public function unmarkTempdata($key)
	{
		if (empty($_SESSION['__ci_vars']))
		{
			return;
		}

		is_array($key) || $key = [$key];

		foreach ($key as $k)
		{
			if (isset($_SESSION['__ci_vars'][$k]) && is_int($_SESSION['__ci_vars'][$k]))
			{
				unset($_SESSION['__ci_vars'][$k]);
			}
		}

		if (empty($_SESSION['__ci_vars']))
		{
			unset($_SESSION['__ci_vars']);
		}
	}
public function unmarkTempdata($key)
	{
		if (empty($_SESSION['__ci_vars']))
		{
			return;
		}

		is_array($key) || $key = [$key];

		foreach ($key as $k)
		{
			if (isset($_SESSION['__ci_vars'][$k]) && is_int($_SESSION['__ci_vars'][$k]))
			{
				unset($_SESSION['__ci_vars'][$k]);
			}
		}

		if (empty($_SESSION['__ci_vars']))
		{
			unset($_SESSION['__ci_vars']);
		}
	}
Unmarks temporary data in the session, effectively removing its
lifespan and allowing it to live as long as the session does.

@param string|array $key	Property identifier or array of them