PHP sort positions with null values but maintain structure

Try :

$sort = [];
$null_position = 1;
arsort($data);
foreach ($data as $key => $value){
    while(in_array($null_position,array_column($data,'position'))) {
       $null_position++;
    }
    $sort[$key] = $value['position'] ?? $null_position++;
}
asort($sort);

instead of

$sort = [];

foreach ($data as $key => $value)
    $sort[$key] = $value['position'];

array_multisort($sort, SORT_ASC, $data);

Filling in the missing values before doing a simple usort:

$data = [
    'Amazon'    => ['position' => null],
    'Google'    => ['position' => 1],
    'Ebay'      => ['position' => null],
    'Microsoft' => ['position' => null],
    'Alibaba'   => ['position' => 4]
];

// Find existing positions.
$positions = array_filter(array_column($data, 'position'));
$i = 1;

foreach ($data as &$comp) {
    if ($comp['position']) {
        // Element already has a position, skip to next one.
        continue;
    }
    while (in_array($i, $positions)) {
        // Increment the counter until we find a value not yet taken.
        $i++;
    }
    // Assign the counter value to the current element.
    $comp['position'] = $i++;
}
unset($comp);

// Sort all values with a simple comparison function.
uasort($data, function ($a, $b) { return $a['position'] <=> $b['position']; });

Somewhat fancier:

// Compute the *missing* positions by subtracting the existing positions
// (extracted via array_column) from the set of possible positions
// (generated with range()).
$positions = array_diff(range(1, count($data)), array_filter(array_column($data, 'position')));

// Apply the missing positions to the array elements in order
// (taking positions off the beginning with array_shift).
array_walk($data, function (&$i) use (&$positions) {
    if (!$i['position']) {
        $i['position'] = array_shift($positions);
    }
});

// Sort all values with a simple comparison function.
uasort($data, function ($a, $b) { return $a['position'] <=> $b['position']; });

Solved.

Not sure if this is the best approach, but the output is the desired.

// Create three arrays to save the positions being used, etc
$itemsWithoutPosition = [];
$itemsWithPosition = [];
$listOfPositionsUsed = [];

// First grab the positions used
foreach ($original as $key => $value)
{
    if ($value['position'])
    {
        $itemsWithPosition[$key] = ['position' => $value['position']];
        array_push($listOfPositionsUsed, $value['position']);
    }
}

// Function to find the next available position
function findAvailablePosition($listOfPositionsUsed)
{
    for ($i = 1; $i <= 5; $i++)
    {
        if (in_array($i, $listOfPositionsUsed))
            continue;

        return $i;
    }
}

// Loop through the items that do not have position set
foreach ($original as $key => $value)
{
    if (!$value['position'])
    {
        $position = findAvailablePosition($listOfPositionsUsed);
        $itemsWithoutPosition[$key] = ['position' => $position];

        array_push($listOfPositionsUsed, $position);
    }
}

// Merge both results
$result = array_merge($itemsWithPosition, $itemsWithoutPosition);

// Sort the results 
array_multisort($result, SORT_ASC);

// Voilá
Array
(
    [Google] => Array
        (
            [position] => 1
        )

    [Amazon] => Array
        (
            [position] => 2
        )

    [Ebay] => Array
        (
            [position] => 3
        )

    [Alibaba] => Array
        (
            [position] => 4
        )

    [Microsoft] => Array
        (
            [position] => 5
        )

)

I was able to achieve it with two for loops and a temp table. The $data_full is the table that we'll be working on. And the $data is the table that'll be containing only the data coming from the database.

https://wtools.io/php-sandbox/b0hU

$data_full = 
[
    'Amazon'    => ['position' => null],
    'Google'    => ['position' => null],
    'Ebay'      => ['position' => null],
    'Microsoft' => ['position' => null],
    'Alibaba'   => ['position' => null]
];

$data = 
[
    'Amazon'    => ['position' => null],
    'Google'    => ['position' => null],
    'Ebay'      => ['position' => null],
    'Microsoft' => ['position' => null],
    'Alibaba'   => ['position' => null]
];

$data['Google']['position'] = 1;
$data['Alibaba']['position'] = 4;

$sort = [];

$num = 1;
foreach ($data_full as $key => $value) { // Loop through the table we're going to insert in
    foreach($data as $key2 => $value2) { // Loop through the table containing results from the DB
        if($data[$key2]['position']==$num) { // If it exists, we insert it, and increment the number by 1, and then continue the first loop
            $data_full[$key]['position'] = $data[$key2]['position'];
            $num++;
            continue 2;
        }
    }
    $data_full[$key]['position'] = $num;
    $num++;
}
var_dump($data_full);