Grouping Associative Arrays by Column Value While Preserving Keys

Consider an array of associative arrays, each representing an entity with attributes like 'id' and 'name'. The challenge is to group these arrays based on a specific column, 'id', while maintaining the original keys.

To achieve this, we can use PHP's foreach loop to iterate over the array. For each inner array, we extract the 'id' value and use it as the index of a new associative array. Within this new array, we assign the original key as the index and the inner array as the value.

$arr = array();

foreach ($old_arr as $key => $item) {
   $arr[$item['id']][$key] = $item;
}

Finally, we use ksort() to sort the resulting array numerically, ensuring that the groups are presented in ascending order of 'id'.

ksort($arr, SORT_NUMERIC);

The output will be an array where each element represents a group of entities with the same 'id' value, while the original keys are preserved within each group.