"string", "sub-nstring" => "?string", "sub-bool" => "bool", "sub-nbool" => "?bool", ]; /** @var string */ private $ppSubString, $ppSubNstring; /** @var bool */ private $ppSubBool, $ppSubNbool; function getSubData(): array { $topData = $this->getTopData(); $subData = [$this->ppSubString, $this->ppSubNstring, $this->ppSubBool, $this->ppSubNbool]; return array_merge($topData, $subData); } }