Custom Array Sorting by input string and position

I have an array. It' looks like:

$arr = [
   '0' => ['id'=>9, 'q'=>'motor', 'pos'=>1],
   '1' => ['id'=>10, 'q'=>'NULL', 'pos'=>0],
   '2' => ['id'=>7, 'q'=>'motor', 'pos'=>2],
   '3' => ['id'=>8, 'q'=>'NULL',  'pos'=>0],
   '4' => ['id'=>11, 'q'=>'motor','pos'=>3],
   '5' => ['id'=>11, 'q'=>'exhaust','pos'=>1]
];

How can I sort the data above to make it looks like (if q='motor' is inside search string):

 $arr = [
       '0' => ['id'=>9, 'q'=>'motor', 'pos'=>1],
       '2' => ['id'=>7, 'q'=>'motor', 'pos'=>2],
       '4' => ['id'=>11, 'q'=>'motor','pos'=>3],
       '1' => ['id'=>10, 'q'=>'NULL', 'pos'=>0],
       '3' => ['id'=>8, 'q'=>'NULL',  'pos'=>0],
       '5' => ['id'=>11, 'q'=>'exhaust','pos'=>1]
    ];

So:

function custom_sort($input_query, $arr) {
   foreach($arr as $key=>$row) {
      if (strpos($input_query, $row['q'])) {
          ... How to Sort By Pos?
      }
   }
}

Thanks!

Updated (question/answer) p.s: I'm trying to use custom variable as input: $q

usort($arr, function($a, $b) use ($q) {
        if ($a['q'] == $q) {
            if($b['q'] == $q) {
                return ($a['pos'] > $b['pos']) ? 1 : -1;
            }
            return -1;
        }
        if ($b['q'] == $q) {
            return 1;
        }
        return 0;
    });

And the function stop working. How can I solve this?

Here's a usort that handles your requirements, wrapped in a function that transforms the array in place:

1. Items with q key containing $query will be placed at the front of the array.

2. Items with q key containing $query will be sorted ascending by their pos value.

3. Everything else will be sorted by its pos value.

function custom_sort($query, &$arr) {
    usort($arr, function($a, $b) use ($query) {
        $in_a = strpos($a['q'], $query) !== false;
        $in_b = strpos($b['q'], $query) !== false;

        if ($in_a && !$in_b) {
            return -1;
        }
        if (!$in_a && $in_b) {
            return 1;
        }

        return $a['pos'] - $b['pos'];
    });
}

custom_sort("motor", $arr);