system/Session/Session.php
public function set($data, $value = null)
	{
		if (is_array($data))
		{
			foreach ($data as $key => &$value)
			{
				if (is_int($key))
				{
					$_SESSION[$value] = null;
				}
				else
				{
					$_SESSION[$key] = $value;
				}
			}

			return;
		}

		$_SESSION[$data] = $value;
	}
public function set($data, $value = null)
	{
		if (is_array($data))
		{
			foreach ($data as $key => &$value)
			{
				if (is_int($key))
				{
					$_SESSION[$value] = null;
				}
				else
				{
					$_SESSION[$key] = $value;
				}
			}

			return;
		}

		$_SESSION[$data] = $value;
	}
Sets user data into the session.

If $data is a string, then it is interpreted as a session property
key, and  $value is expected to be non-null.

If $data is an array, it is expected to be an array of key/value pairs
to be set as session properties.

@param string|array $data  Property name or associative array of properties
@param string|array $value Property value if single key provided