This API that lets you sort this kind of list and present back a description of how to complete your journey.
1 . Run composer install and include autoload file
require '../vendor/autoload.php';
2 . Pass your boarding cards to Boarding class
$train = new Train(
'Madrid',
'Barcelona',
'78A',
'45B'
);
$bus = new Bus(
'Barcelona',
'Gerona'
);
$plane = new Plane(
'Gerona',
'Stockholm',
'SK455',
'45B',
'3A',
'344'
);
$boarding = new Boarding($train, $bus, $plane);
3 . Sort your bordering cards using CardSorter
$sorter = new CardSorter();
$boarding->sortCards($sorter);
4 . Output sorted cards using toHtml method
echo $boarding->toHtml();