Group and merge array row data based on one column

Question

I have an array a bit like:

Array (    
        [1] => Array
            (
                [1] => 21
                [2] => 3
                [0] => Analyst
            )    
        [2] => Array
            (
                [1] => 47
                [2] => 8
                [0] => Catalysis
            )

        [3] => Array
            (
                [1] => 1
                [2] => 0
                [0] => Biomaterials 
            )

        [4] => Array
            (
                [3] => 12
                [4] => 2
                [0] => Analyst
            )

       [5] => Array
            (
                [5] => 12
                [6] => 2
                [0] => Analyst
            )
...

However I would like to renumber those entries with the same [0] value so that I end up with

       [1] => Array
            (
                [1] => 21
                [2] => 3
                [3] => 12
                [4] => 2
                [5] => 12
                [6] => 2
                [0] => Analyst
            )

So far I've tried getting the [0] values out of the $results array by putting them in their own array and saying if you're already there then add [3] and [4] to where [1] and [2] are in a new array but it's not working.

$final = array();
$jArray = array();

foreach($results as $key => $result) {
  if(!in_array($result[0],$jArray) && !empty($result[0])) {
    $jArray[$i] = $result[0];
    $i++;
  }
}



for($x = 0; $x < count($results); $x++) { 
      $k = array_search($results[$x][0],$jArray);
    if(!isset($results[$x][1])) 
      $final[$k][1] = $results[$x][1];
    if(!isset($results[$x][2])) 
      $final[$k][2] = $results[$x][2];    
    if(!isset($results[$x][3])) 
      $final[$k][3] = $results[$x][3];
   if(!isset($results[$x][4])) 
      $final[$k][4] = $results[$x][4];
    if(!isset($results[$x][5]))     
      $final[$k][5] = $results[$x][5];
    if(!isset($results[$x][6]))     
      $final[$k][6] = $results[$x][6];
}

Any simpler ways of doing this?

Answer 1

You can do this way...

$new_arr=array();
$arkeys = array_unique(array_map(function ($v){ return $v[0];},$arr));
foreach($arr as $k=>$arr1)
{
            $new_arr[$arr1[0]][]=array_slice($arr1,0,count($arr1)-1);
}

foreach($arkeys as $v)
{
$new_arr[$v] = call_user_func_array('array_merge', $new_arr[$v]);
}
print_r($new_arr);

OUTPUT :

Array
(
    [Analyst] => Array
        (
            [0] => 21
            [1] => 3
            [2] => 12
            [3] => 2
            [4] => 12
            [5] => 2
        )

    [Catalysis] => Array
        (
            [0] => 47
            [1] => 8
        )

    [Biomaterials] => Array
        (
            [0] => 1
            [1] => 0
        )

)

Working Demo

Answer 2

If you just want to group by the first element of the sub array, a single loop is enough:

$result = array();

foreach ($array as $sub_arr) {
  $key = $sub_arr[0];
  unset($sub_arr[0]);
  if (!isset($result[$key])) {
    $result[$key] = array();
  }
  $result[$key] += $sub_arr;
}

Answer 3

Here

$final = array();

foreach($results as $key => $result) {
  if (!in_array($result[0], array_keys( $final ) ) && !empty($result[0])) {
    $final[$result[0]] = array( $result[0] );
  }
  foreach($result as $k => $v) {
    if ($k != 0 && isset($v)) {
      $final[$result[0]][$k] = $v;
    }
  } 
}