emagister / collections

2.0.4 2026-10-06 06:33 UTC

Requires

• php: ^8.1

Requires (Dev)

• friendsofphp/php-cs-fixer: ^3.0
• infection/infection: ^0.29
• phpunit/phpunit: ^10.5
• squizlabs/php_codesniffer: ^3.0

MIT

Published on Packagist.org on 2026-10-06 06:33 UTC

README

Writing your own typed collection

Methods that return a new sequence (filter(), slice(), tail(), diff(), clone(), ...) build it through createSequence(), which calls the constructor of the current class:

Base class	createSequence() calls
Collection, Map	new static($elements)
HCollection, HMap	new static($type, $elements)
SpecificCollection, SpecificMap	new static($elements)

To write a typed collection whose constructor takes the elements as its first parameter, extend SpecificCollection (or SpecificMap) and pass the type to the parent constructor:

/** @extends SpecificCollection<ConcreteObject> */
final class ConcreteObjectCollection extends SpecificCollection
{
    public function __construct(array $elements = [])
    {
        parent::__construct(ConcreteObject::class, $elements);
    }
}

The constructor can take more parameters, as long as they are optional. Keep in mind that the sequences returned by filter(), slice(), etc. are created with the default values of those parameters, not with the values of the original sequence.

If the constructor cannot be called as shown in the table above, because it has other required parameters or takes its arguments in a different order, you must also override createSequence(). Otherwise those methods throw a CollectionException telling you to do so. Override it as well if the sequences returned by those methods must keep the values of the optional parameters. For example, for a constructor __construct(string $type, array $elements, Logger $logger):

protected function createSequence(array $elements): static
{
    return new static($this->type(), $elements, $this->logger);
}