Laravel.io
<?php

namespace App\Services\Assignment;

use App\Models\Assignment;
use App\Models\Role;
use App\Notifications\Assignment\ParticipantAssigned;
use Illuminate\Support\Facades\Notification;

class ParticipantsNotificationsSender
{
    public function execute(Assignment $assignment, array $participants)
    {
        $this->notifyParticipants($assignment, $participants);

        $this->notifyAccountants($assignment, $participants);
    }

    private function notifyParticipants(Assignment $assignment, array $participants): void
    {
        foreach ($participants as $participant) {
            $participant->user->notify(
                new ParticipantAssigned($assignment, $participant->role)
            );
        }
    }

    private function notifyAccountants(Assignment $assignment, array $participants)
    {
        $accountants = Role::whereIn('name', ['Accounting Manager', 'Accounting Officer'])->get()->pluck('users')->flatten();

        Notification::send(
            $accountants,
            new \App\Notifications\Assignment\Accounting\ParticipantAssigned($assignment, $participants)
        );
    }
}

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