I have a multidimensional array and want to sort it by distance:

```
[clustermarkers] => [
            0 => [
                    0 => [
                      'name' => 'A',
                      'distance' => 10
                    ]
            ],
            1 => [
                    0 => [
                      'name' => 'B',
                      'distance' => 8
                    ]
            ],
            ...
];

```

I have tried usort function, but something wrong:

```
usort($clustermarkers, function($a, $b) {
   return (int)$a['distance'] - (int)$b['distance'];
});

```