PHP多维数组排序将一个元素值保持在第一位置

Question

I have a multidimensional array named $newArray have below values:

$newArray = 
   (
    [0] => Array
        (
            [CountryID] => 24
            [val] => 1
            [PostID] => 1
            [id] => 0
        )

    [1] => Array
        (
            [CountryID] => 355
            [val] => 0.1
            [PostID] => 2
            [id] => 1
        )

    [2] => Array
        (
            [CountryID] => 241
            [val] => 0.3
            [PostID] => 3
            [id] => 2
        )

    [3] => Array
        (
            [CountryID] => 135
            [val] => 0.02
            [PostID] => 4
            [id] => 3
        )

    [4] => Array
        (
            [CountryID] => 24
            [val] => 0.003
            [PostID] => 5
            [id] => 4
        )

    [5] => Array
        (
            [CountryID] => 355
            [val] => 5
            [PostID] => 6
            [id] => 5
        )

    [6] => Array
        (
            [CountryID] => 355
            [val] => 4
            [PostID] => 23
            [id] => 6
        )

    [7] => Array
        (
            [CountryID] => 24
            [val] => 2
            [PostID] => 1
            [id] => 7
        )

    [8] => 
)

I want to sort [CountryID] in DESC, [val] in DESC order only after filtering one element value "24" of [CountryID] on top (with [val] DESC of course), so result should be below:

$newArray = 
    (
        [1] => Array
            (
                [CountryID] => 24
                [val] => 2
                [PostID] => 1
                [id] => 7
            )

        [2] => Array
            (
                [CountryID] => 24
                [val] => 1
                [PostID] => 1
                [id] => 0
            )       

        [3] => Array
            (
                [CountryID] => 24
                [val] => 0.003
                [PostID] => 5
                [id] => 4
            )

        [4] => Array
            (
                [CountryID] => 355
                [val] => 5
                [PostID] => 6
                [id] => 5
            )

        [5] => Array
            (
                [CountryID] => 355
                [val] => 4
                [PostID] => 23
                [id] => 6
            )

        [6] => Array
            (
                [CountryID] => 355
                [val] => 0.1
                [PostID] => 2
                [id] => 1
            )

        [7] => Array
            (
                [CountryID] => 241
                [val] => 0.3
                [PostID] => 3
                [id] => 2
            )

        [8] => Array
            (
                [CountryID] => 135
                [val] => 0.02
                [PostID] => 4
                [id] => 3
            )   

    )

What function I should use here in order to sort a multidimensional array with above order and condition?

I am still learning arrays in php and limited knowledge of that.

Answer 1

You can extract value which you need later, and filter the array to avoid warning.

$inputSearch = 24;
$k = array_keys(array_column($newArray, 'CountryID'), 24);    
foreach($k as $v){
    $temp[] = $newArray[$v];    
    unset($newArray[$v]);
}
array_multisort(array_column($temp, 'val'), SORT_DESC, $temp);
$newArray = array_filter($newArray);
array_multisort(array_column($newArray, 'CountryID'), SORT_DESC,array_column($newArray, 'val'),      SORT_DESC,$newArray);
$newArray = array_merge($temp , $newArray);                
print_r($newArray);

array_column - Return the values from a single column in the input array
array_filter - Filters elements of an array using a callback function
array_search — Searches the array for a given value and returns the first corresponding key if successful
array_multisort — Sort multiple or multi-dimensional arrays
array_unshift — Prepend one or more elements to the beginning of an array
array_keys — Return all the keys or a subset of the keys of an array

Demo .

Output

Array
(
    [0] => Array
        (
            [CountryID] => 24
            [val] => 2
            [PostID] => 1
            [id] => 7
        )

    [1] => Array
        (
            [CountryID] => 24
            [val] => 1
            [PostID] => 1
            [id] => 0
        )

    [2] => Array
        (
            [CountryID] => 24
            [val] => 0.003
            [PostID] => 5
            [id] => 4
        )

    [3] => Array
        (
            [CountryID] => 355
            [val] => 5
            [PostID] => 6
            [id] => 5
        )

    [4] => Array
        (
            [CountryID] => 355
            [val] => 4
            [PostID] => 23
            [id] => 6
        )

    [5] => Array
        (
            [CountryID] => 355
            [val] => 0.1
            [PostID] => 2
            [id] => 1
        )

    [6] => Array
        (
            [CountryID] => 241
            [val] => 0.3
            [PostID] => 3
            [id] => 2
        )

    [7] => Array
        (
            [CountryID] => 135
            [val] => 0.02
            [PostID] => 4
            [id] => 3
        )

)

Answer 2

Using usort you can solve your problem. Example:

usort($newArray, function($a, $b) {
    if ($a['CountryID'] == 135 OR $b['CountryID'] == 135) return 1;
    $retval = $b['CountryID'] - $a['CountryID'];
    if ($retval == 0) {
        $retval = $b['val'] - $a['val'];
    }
    return $retval;
});

echo '<pre>', print_r($newArray);