use array_multisort in multidimensional array

Question

I have an array A with these value

array(
  0 => 'D003',
  1 => 'P001',
  2 => 'P002',
  3 => 'D001'
);

and I have another multidimensional array B with these values

 array(
      0 => 
        array(
          'waypoint_id' => 'D001',
          'count' => '5'),
      1 => 
        array(
          'waypoint_id' => 'D003',
          'count' => '1'),
      2 => 
        array(
          'waypoint_id' => 'P001',
          'count' => '2'),
      3 => 
        array(
          'waypoint_id' => 'P002',
          'count' => '1')
    );   

how to use array_multisort so that I can get my array B to be like these (same order as array B)

  array(
      0 => 
        array(
          'waypoint_id' => 'D003',
          'count' => '1'),
      1 => 
        array(
          'waypoint_id' => 'P001',
          'count' => '2'),
      2 => 
        array(
          'waypoint_id' => 'P002',
          'count' => '1'),
      3 => 
        array(
          'waypoint_id' => 'D001',
          'count' => '5')
    );

Answer 1

I'm not sure array_multisort() can help you here, as the contents of A aren't in any obvious order.

I'd do it by indexing B by waypoint purely for efficiency, and then creating a new $ordered array from A:

$indexed = array();
foreach($b as $array) {
    $indexed[$array['waypoint_id']] = $array;
}

$ordered = array();
foreach($a as $waypoint) {
    $ordered[] = $indexed[$waypoint];
}