PHP Sort Multidimensional array by value which has NULL using uasort

Question

i have created an arry like

$arr[0]['ref']=5;
$arr[0]['name']='name0';

$arr[1]['ref']=6;
$arr[1]['name']='name1';

$arr[2]['ref']=4;
$arr[2]['name']='name2';

$arr[3]['ref']='';
$arr[3]['name']='name3';

$arr[4]['ref']='9';
$arr[4]['name']='name4';

$arr[5]['ref']=''
$arr[5]['name']='name5'

I want to sort this array like using ref value

$arr[2]['ref']=4;
$arr[2]['name']='name2';

$arr[0]['ref']=5;
$arr[0]['name']='name0';

$arr[1]['ref']=6;
$arr[1]['name']='name1';

$arr[4]['ref']='9';
$arr[4]['name']='name4';

$arr[3]['ref']='';
$arr[3]['name']='name3';

$arr[5]['ref']=''
$arr[5]['name']='name5'

i tried

uasort($arr, function($a, $b){
    return $a['ref'] - $b['ref'];
});

But '' values are coming at the beginning. How can I push '' down.

Thanks in advance. I am beginner. please excuse me if i am asking very simple question

Answer 1

This will do the job:

uasort($arr, function($a, $b){
    if ($a['ref'] == "") return 1;
    if ($b['ref'] == "") return -1;
    return $a['ref'] - $b['ref'];
});

Answer 2

You could try

uasort($arr, function($a, $b){
    return -($a['ref'] - $b['ref']);
});

Answer 3

You can add empty values to the end of array using this:

uasort($arr, function($a, $b){
   return $a['ref'] - $b['ref'];
});

//strip empties and move to end
foreach ($arr as $key => $value)
{ 
    if ($value['ref'] == "")
    { 
        unset($arr[$key]);
        $arr[] = $value;
    }
}

// rebuild array index
$arr = array_values($arr);

Output:

Array
(
    [0] => Array
        (
            [ref] => 4
            [name] => name2
        )

    [1] => Array
        (
            [ref] => 5
            [name] => name0
        )

    [2] => Array
        (
            [ref] => 6
            [name] => name1
        )

    [3] => Array
        (
            [ref] => 9
            [name] => name4
        )

    [4] => Array
        (
            [ref] => 
            [name] => name5
        )

    [5] => Array
        (
            [ref] => 
            [name] => name3
        )

)