system/Session/Session.php
public function remove($key)
	{
		if (is_array($key))
		{
			foreach ($key as $k)
			{
				unset($_SESSION[$k]);
			}

			return;
		}

		unset($_SESSION[$key]);
	}
public function remove($key)
	{
		if (is_array($key))
		{
			foreach ($key as $k)
			{
				unset($_SESSION[$k]);
			}

			return;
		}

		unset($_SESSION[$key]);
	}
Remove one or more session properties.

If $key is an array, it is interpreted as an array of string property
identifiers to remove. Otherwise, it is interpreted as the identifier
of a specific session property to remove.

@param string|array $key Identifier of the session property or properties to remove.