<?php

function lowestNumber(array $prices): array
{
    $lowestNumber = ['number' => 0, 'index' => 0];

    for ($i = 0; $i < count($prices); $i++) {
        $lowest = $lowestNumber['number'];

        if ($lowest === 0 || $lowest > $prices[$i]) {
            $lowestNumber = ['number' => $prices[$i], 'index' => $i];
        }
    }

    return $lowestNumber;
}

function clockwise(array $prices): int
{
    $lowest = lowestNumber($prices);
    if ($lowest['index'] + 1 >= count($prices)) {
        throw new \Exception('Не переживай, Биткоин поднимется!');
    }

    $largest = max(array_splice($prices, $lowest['index']));
    if (!$largest) {
        throw new \Exception('Woops?!');
    }

    return $largest - $lowest['number'];
}

function tests()
{
    assert(clockwise([9, 8, 6, 7, 11, 10]) === 5);

    try {
        clockwise([9, 8, 6, 7, 11, 5]);
    } catch (\Exception $e) {
        assert($e->getMessage() === 'Не переживай, Биткоин поднимется!');
    }

    assert(clockwise([3, 9, 8, 6, 7, 12, 10]) === 9);
}

tests();