The property ... is not readable because it is typed "string". But why?

Question

PHP

I used a new php7.4 feature - strict typing of variables, but gives an error

The property "App\Entity\Conference::$slug" is not readable because it is typed "string". You should either initialize it or make it nullable using "?string" instead.

Wherein

private ?string $slug;
// ...
public function getSlug(): ?string
    {
        return $this->slug;
    }

    public function setSlug(string $slug): self
    {
        $this->slug = $slug;

        return $this;
    }

Answer 1

Found. For those who run into this, the reason is that the language designers consider it bad practice to default null to an empty property that they won't support.
private ?string $slug = null;

Answer 2

If a typed property does not have a default value, no implicit null default value is implied (even if the property is nullable). Instead, the property is considered to be uninitialized. Reads from uninitialized properties will generate a TypeError

https://wiki.php.net/rfc/typed_properties_v2#unini...