core-bundle/src/Resources/contao/dca/tl_page.php
public function setRootType(Contao\DataContainer $dc)
	{
		if (Contao\Input::get('act') != 'create')
		{
			return;
		}

		// Insert into
		if (Contao\Input::get('pid') == 0)
		{
			$GLOBALS['TL_DCA']['tl_page']['fields']['type']['default'] = 'root';
		}
		elseif (Contao\Input::get('mode') == 1)
		{
			$objPage = $this->Database->prepare("SELECT * FROM " . $dc->table . " WHERE id=?")
									  ->limit(1)
									  ->execute(Contao\Input::get('pid'));

			if ($objPage->pid == 0)
			{
				$GLOBALS['TL_DCA']['tl_page']['fields']['type']['default'] = 'root';
			}
		}
	}
public function setRootType(Contao\DataContainer $dc)
	{
		if (Contao\Input::get('act') != 'create')
		{
			return;
		}

		// Insert into
		if (Contao\Input::get('pid') == 0)
		{
			$GLOBALS['TL_DCA']['tl_page']['fields']['type']['default'] = 'root';
		}
		elseif (Contao\Input::get('mode') == 1)
		{
			$objPage = $this->Database->prepare("SELECT * FROM " . $dc->table . " WHERE id=?")
									  ->limit(1)
									  ->execute(Contao\Input::get('pid'));

			if ($objPage->pid == 0)
			{
				$GLOBALS['TL_DCA']['tl_page']['fields']['type']['default'] = 'root';
			}
		}
	}
Make new top-level pages root pages

@param Contao\DataContainer $dc