Fields::markChanged

protected function markChanged($name, $value)
{
	$originalValuesIndex = array();
	if (!empty($this->originalValues))
	{
		foreach(array_keys($this->originalValues) as $originalKey)
		{
			$originalValuesIndex[$originalKey] = true;
		}
	}

	$oldValue = $this->get($name);
	if ($oldValue != $value || ($oldValue === null && $value !== null))
	{
		if (!isset($originalValuesIndex[$name]))
		{
			$this->originalValues[$name] = $this->get($name);
		}
		elseif ($this->originalValues[$name] == $value)
		{
			unset($this->changedValues[$name]);
			unset($this->originalValues[$name]);
			return true;
		}

		$this->changedValues[$name] = true;
		return true;
	}

	return false;
}