Collections (opens new window) come from the Laravel (opens new window) ecosystem, and provide a fluid way of working with array-like data.

You can create a Collection anywhere:

{% set list = collect(['Green', 'Teal', 'Blue']) %}

Collections can be used in most situations that an array would be:

  {% for color in colors %}
    {# `color` is one of our original three strings: #}
    <li>{{ color }}</li>
  {% endfor %}

If a collection is created from an array that contains only elements, an ElementCollection is returned, instead.

# Methods

Dozens of convenience methods (opens new window) are available on every collection to simplify cumbersome or error-prone operations.

These methods can be chained together to process data in an elegant way. Take this average review score logic:

{% set recentReviews = craft.entries()
    targetElement: product,
  .postDate(">= #{now|date_modify('-1 month')}")
  .collect() %}

{{ recentReviews.pluck('rating').average() }}

Not all collection methods return another collection! In this example, .pluck() (opens new window) does (containing just the rating field values), but .average() (opens new window) doesn’t (instead returning a float (opens new window)). As Collections are intended for working with lists, methods that return scalar values can only be used at the “end” of a chain.

If at any point you need a plain array from a collection, call its .all() method.

Some common array-manipulation features are already implemented in Craft as Twig filters or functions, but equivalent methods are usually available via Collections. Their supported arguments and signatures may differ slightly, so consult the documentation if you are combining or switching between features.

One common problem, however, is that Twig’s default configuration does not parse anonymous functions or “closures” in every expression context. The nystudio107/craft-closure package (opens new window) provides a shim to work around this limitation.

# Element Collections

Use the .collect() query execution method (in place of .all()) to return elements as a special craft\elements\ElementCollection (opens new window). You can also wrap an existing list of elements with collect(), and Craft will automatically return an ElementCollection:

{# These produce the same results: #}
{% set posts = craft.entries().section('news').collect() %}
{% set posts = collect(craft.entries().section('news').all()) %}

Eager-loaded elements are also wrapped in an ElementCollection that allows them to behave a bit like an element query—you can safely call .all() on any relational field without worrying about whether it was eager-loaded or not—or use .with() to eager-load another set of nested elements!

Element collections have a few extra methods that make them more interoperable with element queries (like the .ids() and .with() methods), or behave more predictably when doing arithmetic (like .merge(), .unique(), or .intersect()):

find(target, default)
Reduce the collection to a single element by passing an element or one or more element IDs.
Eager-loads one or more nested/related sets of elements using the provided map.
contains(key, operator, value)
Behaves identically to the native method, except when used with a single argument. If an element is passed, it is tested against the ID and site ID of each element in the collection; if an integer is passed, it is compared to the ID of each element in the collection.
Returns a new collection containing only the elements’ IDs. Equivalent to .pluck('id').
Combines this set of elements with another one. Any elements in the current collection that share an ID and site ID with an incoming element are replaced. Keys are not preserved.
Re-fetches all elements in the collection from the database. Elements that no longer exist in the database are dropped from list.
Returns elements that are present only in the current collection, as though the incoming elements are “subtracted” from it.
Returns elements present in both the current and incoming lists.
Reduces the collection to elements with unique IDs, via keyBy('id'). For a list of elements with unique IDs and site IDs, use unique('siteSettingsId').
Reduce the collection to elements with the provided ID(s).
Remove elements with the provided ID(s) from the collection.
Render element partials for each element in the collection.