Organizing Associative Array Rows by Column Value

When working with an associative array consisting of subarrays, it is often necessary to reorganize the data based on specific column values. This allows for easier data retrieval and analysis.

Suppose we have an array of subarrays in the following format:

[
    'a' => ['id' => 20, 'name' => 'chimpanzee'],
    'b' => ['id' => 40, 'name' => 'meeting'],
    'c' => ['id' => 20, 'name' => 'dynasty'],
    'd' => ['id' => 50, 'name' => 'chocolate'],
    'e' => ['id' => 10, 'name' => 'bananas'],
    'f' => ['id' => 50, 'name' => 'fantasy'],
    'g' => ['id' => 50, 'name' => 'football']
]

Our goal is to group these subarrays into a new array based on the 'id' field present in each subarray.

To achieve this, we can follow these steps:

1. Initialize an empty array:

$arr = array();

2. Loop through each subarray in the original array. For each subarray, extract its 'id' value and use it as the key in the new array:

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

3. This step sorts the new array by 'id' in ascending order:

ksort($arr, SORT_NUMERIC);

4. Finally, the resulting array is organized by 'id' values:

array
(
    10 => array
          (
            e => array ( id = 10, name = bananas )
          )
    20 => array
          (
            a => array ( id = 20, name = chimpanzee )
            c => array ( id = 20, name = dynasty )
          )
    40 => array
          (
            b => array ( id = 40, name = meeting )
          )
    50 => array
          (
            d => array ( id = 50, name = chocolate )
            f => array ( id = 50, name = fantasy )
            g => array ( id = 50, name = football )
          )
)