src/Queries/ElementQuery.php
protected function fetchAllPropsForSelect()
    {
        $props = [];
        $rsProps = static::$cIblockObject->GetProperties($this->iblockId);
        while ($prop = $rsProps->Fetch()) {
            $props[] = 'PROPERTY_'.$prop['CODE'];
        }

        return $props;
    }
protected function fetchAllPropsForSelect()
    {
        $props = [];
        $rsProps = static::$cIblockObject->GetProperties($this->iblockId);
        while ($prop = $rsProps->Fetch()) {
            $props[] = 'PROPERTY_'.$prop['CODE'];
        }

        return $props;
    }
Fetch all iblock property codes from database

return array