How to properly merge multiple collections in Laravel

Question

I want to merge multiple collections into one. I do have a solution, which is the following:

$allItems = $collection1->merge($collection2)
                        ->merge($collection3)
                        ->merge($collection4)
                        ->merge($collection5);

This actually does work, but I run into problems in cases where some or all of the collections contain no objects. I get an error along the lines of call to merge() on non object.

I actually tried to create an array of all of the collections, and then iterate through them, while checking their validity, but it didn't work and I feel it wasn't very elegant.

How can I elegantly iterate through this process of merging multiple collections, while taking into account that some or all of the collections might be empty or invalid? Appreciated!

Solution 1

What I ended up doing was separating each step. It was the merge chaining that was killing it, because some or all of the collections could have been invalid.

$allItems = new \Illuminate\Database\Eloquent\Collection; //Create empty collection which we know has the merge() method
$allItems = $allItems->merge($collection1);
$allItems = $allItems->merge($collection2);
$allItems = $allItems->merge($collection3);
$allItems = $allItems->merge($collection4);

Solution 2

I had the same question, so I solved it in the following way:

$clients = ClientAccount::query()->get();
$admins = AdminAccount::query()->get();

$users = collect($clients)->merge($admins)->merge($anotherCollection)->merge(...);

Solution 3

I used ->merge() but faced a small issue. So I'm adding this in case anyone else face the same issue. ->concat() is a better solution on database collection merging.

$allItems = new \Illuminate\Database\Eloquent\Collection; 
$allItems = $allItems->concat($collection1);
$allItems = $allItems->concat($collection2);

The reason for this is when merging they take ID of the table as the key. So if two tables have two records with same table id ->merge() will add only one record to $allItems. But ->concat() will add two records as they should.

Solution 4

depend on your data, if collection is actually null or your php support it you can do:

    $allItems = $collection1->merge($collection2 ?: collect())
                    ->merge($collection3 ?: collect())
                    ->merge($collection4 ?: collect())
                    ->merge($collection5 ?: collect());

or you want to do a reduce:

    $allItems = collect([$collection2, $collection3, $collection4])->reduce(function($arr, $item) {
        if (empty($item) || $item->isEmpty())
            return $arr;
        return $arr->merge($item);
    }, $collection1);

or plain php reduce without overhead

    $allItems = array_reduce([
        $collection2,
        $collection3,
        $collection4
    ], function($arr, $item) {
        if (empty($item) || $item->isEmpty())
            return $arr;
        return $arr->merge($item);
    }, $collection1);

View more solutions