Simple implementation of Rails' .to_sentence for PHP

to_sentence.php

<?php

if (! function_exists('to_sentence')) {
    function to_sentence(array $parts, $connector = ', ', $finally = ' and '): string
    {
        switch (count($parts)) {
            case 0:
                return '';
            case 1:
                return reset($parts);
            case 2:
                return reset($parts) . $finally . end($parts);
            default:
                return implode($connector, array_slice($parts, 0, -1)) . $finally .  end($parts);
        }
    }
}