Collection object

v1.7.1 2021-09-26 18:36 UTC

This package is auto-updated.

Last update: 2023-01-26 21:35:58 UTC


This Collection library is best thought of as an "upgraded object-oriented array".

This package provides features to write more beautiful and readable code.


You can install this package to your PHP project with:

composer require markhj/collection

You will need Composer 2.


use Markhj\Collection\Collection;

$collection = new Collection;
$collection->push('John', 'Jane');

$collection->map(function($item) {
	return $item . ' Doe';

var_dump($collection->all()); // John Doe, Jane Doe


public function push(...$objects): Collection;
public function set($key, $object): Collection;
public function add(Collection $collection): Collection;
public function get($key);
public function keyExists($key): bool;
public function all(): array;
public function count(?callable $filter = null): int;
public function empty(): Collection;
public function reverse(): Collection;
public function keys(): Collection;
public function toJson(): string;
public function indexOf($item): ?int;
public function remove(...$keys): Collection;
public function first();
public function last();
public function clone(): Collection;
public function append(Collection $collection): Collection;
public function prepend(Collection $collection): Collection;
public function crop(int $start, int $size): Collection;
public function limit(int $limit): Collection;
public function has($item): bool;
public function hasAllOf(...$items): bool;
public function hasAnyOf(...$items): bool;
public function map(callable $handler): Collection;
public function filter(callable $handler): Collection;
public function forEach(callable $handler): Collection;
public function retrieve(callable $filter): Collection;
public function merge(Collection $target): Collection;
public function mergePreserving(Collection $target): Collection;
public function append(Collection $collection): Collection;
public function prepend(Collection $collection): Collection;
public function before($key, Collection $collection): Collection;
public function after($key, Collection $collection): Collection;
public function isAssociative(): bool;
public function isGraceful(): bool;

There are examples of some of the methods further down.

Associative collection

Associative collections provide all the same functionality as the non-associative, but uses key/value pairing similar to PHP's associative arrays.

$collection = new AssociativeCollection;
$collection->add('order', $order);
$collection->add('customer', $customer);

// ...

$collection->get('customer'); // Returns the customer

Language features


When you typecast the collection to string, it will return the JSON structure of the collection.


You can use the foreach operator on the collection instance.

foreach ($collection as $key => $value) {
	// ...

Example use of other methods


The map method iterates over every element of the collection, and assigns the returned value of the handler to the element in the collection.

$collection = (new Collection)
	->push(1, 2, 3)
	->map(function($item, $key) {
		return $item * 2;

// 2, 4, 6


The forEach method is in many ways similar to the map method, but it will not assign the returned value to the element in the collection. Instead you can carry out actions which aren't directly related to the collection itself.

$sum = 0;
$collection = (new Collection)
	->push(1, 2, 3)
	->forEach(function($item, $key) use(&$sum) {
		return $sum += $item;

// $sum is 6


The sort method sorts the collection elements by a defined handler (callable)

$collection = (new Collection)
	->push(8, 2, 5)
	->sort(function($a, $b) {
		return $a > $b;

// 2, 5, 8


The filter method removes unwanted elements from the collection.

$collection = (new Collection)
	->push(8, 2, 5)
	->filter(function($a) {
		return $a != 2;

// 8, 5


The retrieve method creates a new (cloned) collection based on requested elements. This allows you to extract a filtered subset of elements, without affecting the original collection itself.

$evenNumbers = $collection->retrieve(function($a) {
	return $a % 2 == 0;


The has method returns true if the target item is found in the collection.

$collection = (new Collection)->push(1, 2, 3);
$collection->has(1); // true
$collection->has(8); // false

The has method can also compare objects.


$collection = (new Collection)->push(1, 2, 3);
$collection->hasAnyOf(2, 8); // true
$collection->hasAnyOf(8, 11); // false


$collection = (new Collection)->push(1, 2, 3);
$collection->hasAllOf(2, 3); // true
$collection->hasAllOf(2, 8); // false


With the merge method you can merge another collection into the current.

$a = (new Collection)->push(1, 2, 3);
$b = (new Collection)->push(1, 10, 20, 40);

$a->merge($b); // 1, 10, 20, 40

You can use the mergePreserving to protect the values of the existing collection.

$a = (new Collection)->push(1, 2, 3);
$b = (new Collection)->push(1, 10, 20, 40);

$a->mergePreserving($b); // 1, 2, 3, 40

These methods are closely related to append and prepend.


You can use the "out of the box" collection objects provied in the package, but in many instances it makes sense to write custom collections which inherit the Collection. This allows you to expand with relevant methods.


When you create new collections you might want to restrict it to certain data types. For this, you can override the method

public function validate($item): bool

By default this method always returns true - meaning it accepts any type.

You can for example limit to strings:

public function validate($item): bool
	return is_string($item);

Or to certain class names:

public function validate($item): bool
	return get_class($item) == '...';

If a wrong data type is passed the InvalidItemTypeException is thrown.


For example, you can create a collection of date/time objects, where you add methods to retrieve the earliest and latest instances.

class MyCustomDateCollection extends Collection
	public function earliest()
		// ...

	public function latest()
		// ...

Another example would be a collection of payment methods, where you add methods relevant to your business logic. It could be a boolean method to check for expired credit cards, a method to get all credit cards, or a method to retrieve default payment method.

class PaymentMethodCollection extends Collection
	public function hasExpiredCreditCard(): bool
		// Pseudo/example code to find expired card
		return $this->count(function($paymentMethod) {
			return $paymentMethod->isExpired();
		}) > 0;

	public function getCreditCards(): Collection
		return $this->retrieve(function($paymentMethod) {
			// Logic to determine of $paymentMethod is a credit card
			// or another type

	public function getDefaultPaymentMethod(): ?PaymentMethod
		// Find the default payment method


Graceful handling of missing keys

When you're working on a class inheriting the Collection object, you can set the graceful property to true, to enable graceful handling of trying to access a collection element that doesn't exist. In normal circumstances, trying to access an element that doesn't exist will throw KeyDoesNotExistException. If graceful handling is enabled and you try access a non-existent key NULL will be returned.