PHP How to organize array into groups but keep the order?

Question

I want to make arrays into groups by id,
but still keep the orders, that means it might have duplicate groups, like:

Group1 [id: 1]
Group2 [id: 2]
Group3 [id: 1]
....
...
..
.

Array:

array (
  0 => 
  array (
    'id' => 1,
    'message' => 'AAA',
    'sent_on' => 1582097767
  ),

  1 => 
  array (
    'id' => 2,
    'message' => 'AAAQAW',
    'sent_on' => 1582097770
  ),

  2 => 
  array (
    'id' => 2,
    'message' => 'dqwdq',
    'sent_on' => 1582097772
  ),

  3 => 
  array (
    'id' => 1,
    'message' => 'dqwdq',
    'sent_on' => 1582097773
  ),

  4 => 
  array (
    'id' => 1,
    'message' => 'wq',
    'sent_on' => 1582097773
  ),

  5 => 
  array (
    'id' => 2,
    'message' => 'd',
    'sent_on' => 1582097774
  ),

  6 => 
  array (
    'id' => 1,
    'message' => 'dew',
    'sent_on' => 1582112219
  )
)

Hoped result:

array (
    0 => 
    array (
        0 => 
        array (
          'id' => 1,
          'message' => 'AAA',
          'sent_on' => 1582097767

        ),
    ),

    1 => 
    array (
        0 => 
        array (
          'id' => 2,
          'message' => 'AAAQAW',
          'sent_on' => 1582097770

        ),
        1 => 
        array (
          'id' => 2,
          'message' => 'dqwdq',
          'sent_on' => 1582097772

        )
    ),

    2 => 
    array (
        0 => 
        array (
          'id' => 1,
          'message' => 'dqwdq',
          'sent_on' => 1582097773

        ),
        1 => 
        array (
          'id' => 1,
          'message' => 'wq',
          'sent_on' => 1582097773

        )
    ),

    3 => 
    array (
        0 => 
        array (
          'id' => 2,
          'message' => 'd',
          'sent_on' => 1582097774

        )
    ),

    4 => 
    array (
        0 => 
        array (
          'id' => 1,
          'message' => 'dew',
          'sent_on' => 1582112219

        )
    )
)

@matiit Uh, yes, I only know how to make the array into only two groups like id=1, id=2, but in my hope it need to have five groups — carry0987
– carry0987, Commented Feb 19, 2020 at 16:45

Mihai Matei · Accepted Answer · 2020-02-19 16:54:52Z

1

Yes, it could be done pretty easy by using array_reduce:

$lastCheckedItem = ['id' => 0];

$finalArray = array_reduce($array, static function(array $carry, array $item) use (&$lastCheckedItem) {
    if ($lastCheckedItem['id'] === $item['id'] && !empty($carry)) {
        $lastKey = array_key_last($carry);
        $carry[$lastKey][] = $item;
    }
    else {
        $carry[] = [$item];
    }

    $lastCheckedItem = $item;

    return $carry;
}, []);

answered Feb 19, 2020 at 16:54

Mihai Matei

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4 Comments

carry0987 Over a year ago

Thanks a lot !!! Great answer !! By the way, why the array name is $carry lol

Mihai Matei Over a year ago

yw. Well, because it carries the values set on each iteration until the loop is ended.

carry0987 Over a year ago

Got it. It made me laugh due to it is my english nickname from my dad.

Mihai Matei Over a year ago

yeah.. I noticed it since you asked about it :)

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