也许你想要这样的东西：

// This is an example function to generate initial tickets
function genTickets(int $num): array
{
    $tickets = [];
    for ($i = 0; $i < $num; $i++) {
        $tickets[] = $i + 1;
    }
    return $tickets;
}
function getTicketsSlice(array $tickets, bool $ascending, int $count, int $offset): array
{
    $slice = array_slice($tickets, $offset, $count);
    if (!$ascending) {
        return array_reverse($slice);
    }
    return $slice;
}
function getSoldTicketsWithOpportunities(array $tickets, int $soldTicketsCnt): array
{
    $opportunities = (int)floor((count($tickets) - $soldTicketsCnt) / $soldTicketsCnt);
    $soldTickets = [];
    for ($i = 0; $i < $opportunities; $i++) {
        $ascending = $i % 2 !== 0;
        foreach (getTicketsSlice($tickets, $ascending, $soldTicketsCnt, ($i + 1) * $soldTicketsCnt) as $idx => $sliceItem) {
            $soldTickets[$idx][] = $sliceItem;
        }
    }
    return $soldTickets;
}
$totalTicketsCnt = 60000;
$soldTicketsCnt = 10000;
$tickets = genTickets($totalTicketsCnt);
$soldTickets = getSoldTicketsWithOpportunities($tickets, $soldTicketsCnt);
foreach ($soldTickets as $ticketId => $opportunities) {
    ?>
    <li>
        <span data-oportunidades='<?= json_encode($opportunities, JSON_THROW_ON_ERROR) ?>'>
            <?= str_pad((string)($ticketId + 1), 5, "0", STR_PAD_LEFT) ?>
        </span>
    </li>
    <?php
}

或者以不那么自然而然的方式：

// This is an example function to generate initial tickets
function genTickets(int $num): array
{
    $tickets = [];
    for ($i = 0; $i < $num; $i++) {
        $tickets[] = $i + 1;
    }
    return $tickets;
}
function getTicketsSlice(array $tickets, bool $ascending, int $count, int $offset): array
{
    $slice = array_slice($tickets, $offset, $count);
    if (!$ascending) {
        return array_reverse($slice);
    }
    return $slice;
}
$totalTicketsCnt = 60000;
$soldTicketsCnt = 10000;
$tickets = genTickets($totalTicketsCnt);
// Get tickets slice from 10000 to 20000 in reverse order
foreach (getTicketsSlice($tickets, false, $soldTicketsCnt, 10000) as $sliceItem) {
    $soldTickets[] = [$sliceItem];
}
// Apply next opportunities in ascending order
foreach (getTicketsSlice($tickets, true, $soldTicketsCnt, 20000) as $idx => $sliceItem) {
    $soldTickets[$idx][] = $sliceItem;
}
// Apply next opportunities in descending order
foreach (getTicketsSlice($tickets, false, $soldTicketsCnt, 30000) as $idx => $sliceItem) {
    $soldTickets[$idx][] = $sliceItem;
}
// Apply next opportunities in ascending order
foreach (getTicketsSlice($tickets, true, $soldTicketsCnt, 40000) as $idx => $sliceItem) {
    $soldTickets[$idx][] = $sliceItem;
}
// Apply next opportunities in descending order
foreach (getTicketsSlice($tickets, false, $soldTicketsCnt, 50000) as $idx => $sliceItem) {
    $soldTickets[$idx][] = $sliceItem;
}
foreach ($soldTickets as $ticketId => $opportunities) {
    ?>
    <li>
        <span data-oportunidades='<?= json_encode($opportunities, JSON_THROW_ON_ERROR) ?>'>
            <?= str_pad((string)($ticketId + 1), 5, "0", STR_PAD_LEFT) ?>
        </span>
    </li>
    <?php
}