Group array rows by one column and only create a subarray from another column if more than one value

Question

How can I group row data from a two-dimensional array and only create a subarray of another column if the respective group contains more than one value?

In other words, I need to group rows by id and conditionally restructure an array of arrays to have a variable depth of either 2 or 3 levels.

Input:

[
    ['id' => 567, 'value' => 780],
    ['id' => 676, 'value' => 743],
    ['id' => 676, 'value' => 721],
    ['id' => 234, 'value' => 766],
    ['id' => 234, 'value' => 680]
]

Desired output:

[
    ['id' => 567, 'value' => 780],
    ['id' => 676, 'value' => [743, 721]],
    ['id' => 234, 'value' => [766, 680]]
]

Answer 1

Are you sure you want to have the value as an integer when there is one value and an array when there are more?

<?php
$array = array(
    array('id' => 567, 'value' => 780),
    array('id' => 676, 'value' => 743),
    array('id' => 676, 'value' => 721),
    array('id' => 234, 'value' => 766),
    array('id' => 234, 'value' => 680)
);

foreach ($array as $item) {
    $result[$item['id']][] = $item['value'];
}

foreach ($result as $id => $value) {
    if (count($value) > 1) {
        $output[] = array(
            'id' => $id,
            'value' => $value
        );
    } else {
        $output[] = array(
            'id' => $id,
            'value' => $value[0]
        );
    }
}

echo '<pre>';
print_r($output);
echo '</pre>';
?>

If not

<?php
$array = array(
    array('id' => 567, 'value' => 780),
    array('id' => 676, 'value' => 743),
    array('id' => 676, 'value' => 721),
    array('id' => 234, 'value' => 766),
    array('id' => 234, 'value' => 680)
);

foreach ($array as $item) {
    $result[$item['id']][] = $item['value'];
}

foreach ($result as $id => $value) {
    $output[] = array(
        'id' => $id,
        'value' => $value
    );
}

echo '<pre>';
print_r($output);
echo '</pre>';
?>