where $value in array of $column code example

Example 1: array_column in php

$a = array(
  array(
    'id' => 5698,
    'first_name' => 'Peter',
    'last_name' => 'Griffin',
  ),
  array(
    'id' => 4767,
    'first_name' => 'Ben',
    'last_name' => 'Smith',
  ),
  array(
    'id' => 3809,
    'first_name' => 'Joe',
    'last_name' => 'Doe',
  )
);

$last_names = array_column($a, 'last_name');
print_r($last_names);

Example 2: php collapse common columns in associative array

/* Collapse on common columns which is also the new key e.g.
([0] => [[id] => 1234, [firstName] => "foo", [1] => [[id] => 1234, [lastName] => "bar")
will become ([1234] => [[firstName] => "foo", [lastName]="bar"]
Credit to https://stackoverflow.com/users/762073/xdazz
*/
$result = array();
foreach ($data as $element) {
    $result[$element['id']][] = $element;// [] appends to the array if it already exists
}