php - split an array evenly depend on the number of the giving years

Solution:

This solves it slightly differently.
First is to split up the even segments, this is the first set of elements which are split with the same amount of elements(so the first 2 items in your example). Also note that instead of usingceil(), I usefloor() to round down the value.

Then the remaining elements are added in one chunk to the end of the array.

function planner($courses, $periodicity, $preserve_keys = false)
{
    $nbrDays = (int) floor(count($courses) / $periodicity);

    if ($nbrDays > 0) {
        $initialSplit = array_slice($courses, 0, $nbrDays * ($periodicity - 1), $preserve_keys);
        $split = array_chunk($initialSplit, $nbrDays, $preserve_keys);
        // Add in the remaining elements
        $split[] = array_slice($courses, $nbrDays * ($periodicity - 1), null, $preserve_keys);
        return $split;
    }
    return $courses;
}
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Solution:

You can very easily spread with modulus. But the complicated thing is to put the remaining at bottom.

$planner = function (array $plans, int $periods): array {
    $result = [];
    $i      = 0;
    $remain = count($plans) % $periods;
    $last   = count($plans) - $remain;
    while ($plan = current($plans)) {
        if ($last === $i) break;
        $result[$i++ % $periods][] = $plan;
        next($plans);
    }
    while ($remain-- > 0) {
        $result[$i - 1][] = current($plans);
        next($plans);
    }
    return $result;
};

echo json_encode($planner(['php', 'mysql', 'java', 'ruby'], 1)), "\n";
echo json_encode($planner(['php', 'mysql', 'java', 'ruby'], 2)), "\n";
echo json_encode($planner(['php', 'mysql', 'java', 'ruby'], 3)), "\n";
echo json_encode($planner(['php', 'mysql', 'java', 'ruby'], 4)), "\n";
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Output

[["php","mysql","java","ruby"]]
[["php","java"],["mysql","ruby"]]
[["php"],["mysql"],["java","ruby"]]
[["php"],["mysql"],["java"],["ruby"]]
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Alternative version with different result

Here a simpler version, if you don't need the rest have in the bottom.

$planner = function (array $plans, int $periods): array {
    $result = [];
    $i      = 0;
    foreach ($plans as $plan) {
        $result[$i++ % $periods][] = $plan;
    }
    return $result;
};

echo json_encode($planner(['php', 'mysql', 'java', 'ruby'], 1)), "\n";
echo json_encode($planner(['php', 'mysql', 'java', 'ruby'], 2)), "\n";
echo json_encode($planner(['php', 'mysql', 'java', 'ruby'], 3)), "\n";
echo json_encode($planner(['php', 'mysql', 'java', 'ruby'], 4)), "\n";
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Output

[["php","mysql","java","ruby"]]
[["php","java"],["mysql","ruby"]]
[["php","ruby"],["mysql"],["java"]]
[["php"],["mysql"],["java"],["ruby"]]
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