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Resetting Laravel Collection Keys After Filtering

April 22nd, 2024

I recently filtered a Laravel collection that was due to be output as JSON. To my surprise, it didn't work as intended. Here's what happened, and how to resolve it!

First up, let's take a look at a basic filtered Collection.

$collection = collect([1, 2, 3, 4, 5]);

dd(json_encode($collection));

The result of this when using json_encode is the following:

[1,2,3,4,5]

Pretty basic stuff, and this is to be expected. However, let's filter this and see what changes.

$collection = collect([1, 2, 3, 4, 5])->filter(function ($number) {
    return $number !== 1;
});

dd(json_encode($collection));

Now, here's the result of the filtered version.

{"1":2,"2":3,"3":4,"4":5}

This can cause unintended side effects if you're passing a collection down to use in JavaScript. In my case, I was directly using the output in Alpine.js and yeah... stuff broke.

The reason for the difference in the structure of the keys in a filtered collection after we've removed an item — they're no longer sequential and therefore treated like properties and values.

The fix is pretty simple. Laravel's Collection class has a handy values method to effectively just return the values of the Collection, and therefore reset the keys back to a sequential order.

So, here's how we'd reset the collection keys after sorting.

$collection = collect([1, 2, 3, 4, 5])->filter(function ($number) {
    return $number !== 2;
})
    ->values();

dd(json_encode($collection));

And now we're back to our familiar output.

[1,3,4,5]

Next time you're doing anything to a Laravel Collection to reduce its size, reach for the values method to reset everything back to normal.

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Author
Alex Garrett-Smith
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