private function isExistingPropertyVirtual(string $propertyName): bool
    {
        assert($this->propertyExists($propertyName));
        return $this->properties[$propertyName] === self::PROPERTY_VIRTUAL;
    }
private function isExistingPropertyVirtual(string $propertyName): bool
    {
        assert($this->propertyExists($propertyName));
        return $this->properties[$propertyName] === self::PROPERTY_VIRTUAL;
    }
private function isExistingPropertyVirtual ( string $ propertyName ) : bool { assert ( $ this -> propertyExists ( $ propertyName ) ) ; return $ this -> properties [ $ propertyName ] === self :: PROPERTY_VIRTUAL ; }
Tell whether or not an existing property is virtual.

@param string $propertyName
@return bool
Tell whether or not an existing property is virtual .