php - php sorting multi arrays with multi priority

Question

I have N number of arrays (eg. 3 arrays):

$arr1 = array(0 => array('id' => 34, 'score' => 440),
          1 => array('id' => 32, 'score' => 140),
          2 => array('id' => 22, 'score' => 121),
          3 => array('id' => 99, 'score' => 532)
    );

$arr2 = array(0 => array('id' => 32, 'score' => 213),
          1 => array('id' => 34, 'score' => 354),
          2 => array('id' => 22, 'score' => 674)
    );

$arr3 = array(0 => array('id' => 34, 'score' => 10),
          1 => array('id' => 22, 'score' => 449),
          2 => array('id' => 99, 'score' => 586),
          3 => array('id' => 32, 'score' => 113),
          4 => array('id' => 16, 'score' => 777)

    );

I want to sort these (N) arrays depending on (id) and (score) but i want to give the priority to the repetition id occurrence in all arrays and then the second priority to the max score, and the result will be (1) filtered unique array which holds unique ids according to these rules of sort.

I tried to do this using php usort function to pass comparison function but i failed to do the job.

Answer 1

If the source of the data comes from a mysql database, this custom sort can be easily retrieved with a simple sql query.

But if we must work with the arrays directly then this should work too: (Sorry for dirty coding and poor mobility.)

$all_arrays = array_merge( $arr1, $arr2, $arr3 ); // merge all arrays into one
$items = $ascores = $scores = $occurs = $sorted_ids = array();
foreach( $all_arrays as $elem ) {
    if(isset($occurs[ $elem['id'] ])) { $occurs[ $elem['id'] ]++; } else { $occurs[ $elem['id'] ] = 1; }
    if( ! isset($ascores[ $elem['id'] ]) || $elem['score'] > max( $ascores[ $elem['id'] ] ) ) { 
        $ascores[ $elem['id'] ][] = $elem['score']; 
        $scores[ $elem['id'] ] = $elem['score']; 
    }
    $items[ $elem['id'] ] = array( 'id'=>$elem['id'], 'maxs'=>$scores[ $elem['id'] ], 'occs'=>$occurs[ $elem['id'] ] );
}

array_multisort( $occurs, SORT_DESC, $scores, SORT_DESC, $items);
/// print_r( $items ); // $items holds unique sorted data. outputs: Array ( [0] => Array ( [id] => 22 [maxs] => 674 [occs] => 3 ) [1] => Array ( [id] => 34 [maxs] => 440 [occs] => 3 ) [2] => Array ( [id] => 32 [maxs] => 213 [occs] => 3 ) [3] => Array ( [id] => 99 [maxs] => 586 [occs] => 2 ) [4] => Array ( [id] => 16 [maxs] => 777 [occs] => 1 ) )

foreach( $items as $item ) $sorted_ids[] = $item['id'];
/// print_r( $sorted_ids ); // $sorted_ids holds your desired ids list. outputs: Array ( [0] => 22 [1] => 34 [2] => 32 [3] => 99 [4] => 16 )