How to sort an array by a value inside the array in php

a_how_to_sort_an_array_by_a_value_inside_the_array.php

uasort($valid_variants_ids, function ($a, $b) {
  // if the first item and the second item have the same value, do nothing.
  if ($a['study_option_weight'] == $b['study_option_weight']) {
    return 0;
  }

  // if the first item is less than the second item, move the first option down by one, otherwise move it up by one.
   return $a['study_option_weight'] < $b['study_option_weight'] ? -1 : 1;
});

b_valid_variants_ids_array_BEFORE_sort.json

Array
(
    [3] => Array
        (
            [id] => 2140
            [revision_id] => 285900
            [start_year_month_weight] => 15
            [study_option_weight] => 0
        )

    [8] => Array
        (
            [id] => 2985
            [revision_id] => 285911
            [start_year_month_weight] => 15
            [study_option_weight] => 1
        )

    [9] => Array
        (
            [id] => 2987
            [revision_id] => 285914
            [start_year_month_weight] => 16
            [study_option_weight] => 3
        )

    [10] => Array
        (
            [id] => 2989
            [revision_id] => 285917
            [start_year_month_weight] => 16
            [study_option_weight] => 0
        )

    [12] => Array
        (
            [id] => 13438
            [revision_id] => 285923
            [start_year_month_weight] => 16
            [study_option_weight] => 4
        )

)

c_valid_variants_ids_array_AFTER_sort.json

Array
(
    [3] => Array
        (
            [id] => 2140
            [revision_id] => 285900
            [start_year_month_weight] => 15
            [study_option_weight] => 0
        )

    [10] => Array
        (
            [id] => 2989
            [revision_id] => 285917
            [start_year_month_weight] => 16
            [study_option_weight] => 0
        )

    [8] => Array
        (
            [id] => 2985
            [revision_id] => 285911
            [start_year_month_weight] => 15
            [study_option_weight] => 1
        )

    [9] => Array
        (
            [id] => 2987
            [revision_id] => 285914
            [start_year_month_weight] => 16
            [study_option_weight] => 3
        )

    [12] => Array
        (
            [id] => 13438
            [revision_id] => 285923
            [start_year_month_weight] => 16
            [study_option_weight] => 4
        )

)