Iterate over a collection in laravel and aggregate it

September 13, 2022

I’ve a sample collection

#items: array:4 [▼
0 => Collection {#465 ▼
  #items: array:2 [▼
    "id" => 1
    "user_id" => 5
  ]
}
1 => Collection {#455 ▼
  #items: array:2 [▼
    "id" => 2
    "user_id" => 5
  ]
}
2 => Collection {#419 ▼
  #items: array:2 [▼
    "id" => 3
    "user_id" => 1
  ]
}
3 => Collection {#410 ▼
  #items: array:2 [▼
    "id" => 4
    "user_id" => 1
  ]
}
]
}

how can I aggregate the above collection to the below collection. It is the count of ids for every user_id’s.

#items: array:2 [▼
0 => Collection {#465 ▼
  #items: array:2 [▼
    "user_id" => 1
    "count" => 2
  ]
}
1 => Collection {#455 ▼
  #items: array:2 [▼
    "user_id" => 5
    "count" => 2
  ]
}
]
}

Any suggestions would be appreciated.

>Solution :

I recreated the collection with the following code.

$collection = collect([
    collect(['id' => 1, 'user_id' => 5]),
    collect(['id' => 2, 'user_id' => 5]),
    collect(['id' => 3, 'user_id' => 1]),
    collect(['id' => 4, 'user_id' => 1]),
]);

Assuming this structure, you can get the results by chaining a few methods.

use Illuminate\Support\Collection;

$collection
    ->groupBy('user_id')
    ->map(fn ($item, $key) => ['user_id' => $key, 'count' => $item->count()])
    ->values();
    // ->mapInto(Collection::class); // if you really need each item to be its own collection