Payment::onBeforeSetFields

protected function onBeforeSetFields(array $values)
{
	if (isset($values['PAID']))
	{
		if ($this->getField('PAID') === 'Y')
		{
			if ($values['PAID'] === 'N')
			{
				$values = ['PAID' => $values['PAID']] + $values;
			}
		}
		else
		{
			if ($values['PAID'] === 'Y')
			{
				// move to the end of array
				unset($values['PAID']);
				$values['PAID'] = 'Y';
			}
		}
	}

	return $values;
}