'datetime', ]; public function send_user() { return $this->belongsTo(User::class, 'sender')->withDefault(['id' => 0, 'username' => 'System']); } public function receive_user() { return $this->belongsTo(User::class, 'receiver'); } public static function add(array $data): self { clear_inbox_count_cache($data["receiver"]); $message = self::query()->create($data); fire_event(ModelEventEnum::MESSAGE_CREATED, $message); return $message; } }