Sort 2d array by column containing float values and the string "N/A" with "N/A" rows moved to the end

Question

My array:

$data = [
    ['id' => 1, 'value' => 1.2],
    ['id' => 3, 'value' => 'N/A'],
    ['id' => 2, 'value' => 2.5],
];

I want sort the rows with numeric value values precede rows with non-numeric value values. (2.5 -> 1.2 -> 'N/A'):

My code:

usort($data, function($a, $b) {
    if ($a['value'] == 'N/A') {
        return $b['value'];
    } elseif ($b['value'] == 'N/A') {
        return $a['value'];
    }

    return strcmp($b['value'], $a['value']);
});

Desired result:

[
    ['id' => 2, 'value' => 2.5],
    ['id' => 1, 'value' => 1.2],
    ['id' => 3, 'value' => 'N/A'],
]

Answer 1

Try this:

<?php
$data = array(
      array(
          'id' => 1,
          'value' => 1.2
      ),
      array(
          'id' => 2,
          'value' => 2.5
      ),
      array(
          'id' => 3,
          'value' => 'N/A'
      )
    );

$value= array();

foreach ($data as $k => $sub_arr) {
    $value[$k] = $sub_arr['value'];
}

array_multisort($value, SORT_DESC, SORT_NUMERIC, $data);
print_r($data);
?>

Output:

$ php -f test.php 
Array
(
    [0] => Array
        (
            [id] => 2
            [value] => 2.5
        )

    [1] => Array
        (
            [id] => 1
            [value] => 1.2
        )

    [2] => Array
        (
            [id] => 3
            [value] => N/A
        )

)

Here we use array_multisort function.

Answer 2

Assuming all of your float values are greater than 0.0, you can cast all values to float-type and order descending without needing to pre-iterate the input array to prepare things.

Code: (Demo)

usort($data, fn($a, $b) => (float) $b['value'] <=> (float) $a['value']);
var_export($data);

---

If you want to explicitly position N/A values at the end, then you can feed two values to compare on each iteration: (Demo)

usort(
    $data,
    fn($a, $b) => [$b['value'] !== 'N/A', $b['value']]
                  <=>
                  [$a['value'] !== 'N/A', $a['value']]
);
var_export($data);