A plain PHP reimplementation of Laravel's higher-order messages.

higher-order-messages.php

<?php

class Participant
{
	public function __construct(private int $teamNumber, public int $score = 0) {}

	public function belongsToTeam(int $teamNumber): bool
	{
		return $this->teamNumber === $teamNumber;
	}
}

class HigherOrderCollectionProxy
{
	public function __construct(private $collection, private string $collMethod) {}

	public function __call(string $method, array $parameters)
	{
		return $this->collection->{$this->collMethod}(fn($value) => $value->{$method}(...$parameters));
	}

	public function __get(string $key)
	{
		return $this->collection->{$this->collMethod}(fn($value) => $value->{$key});
	}
}


class MyCollection
{
	public function __construct(private array $items = []) {}

	public function __get(string $key)
	{
		return new HigherOrderCollectionProxy($this, $key);
	}

	public function filter(callable $callback): static
	{
		return new static(array_filter($this->items, $callback));
	}

	public function sum(callable $callback): int|float
	{
		return array_reduce($this->items, fn($result, $item) => $result + $callback($item), 0);
	}
}

$participants = new MyCollection([
	new Participant(teamNumber: 1, score: 11),
	new Participant(teamNumber: 1, score: 6),
	new Participant(teamNumber: 2, score: 5),
	new Participant(teamNumber: 2, score: 8),
	new Participant(teamNumber: 2, score: 7),
	new Participant(teamNumber: 3, score: 20),
]);

$team2Participants = $participants->filter(fn($participant) => $participant->belongsToTeam(2));

$totalScore = $team2Participants->sum(fn($participant) => $participant->score);

// chaining
$totalScore = $participants
	->filter(fn($participant) => $participant->belongsToTeam(2))
	->sum(fn($participant) => $participant->score);

// Higher Order Messages

$team2Participants = $participants->filter->belongsToTeam(2);

$totalScore = $team2Participants->sum->score;

// chaining
$currentYearAmount = $participants->filter->belongsToTeam(2)->sum->score;