Why construct method gives errors inside class file – PHP

I just opened new project and this is class file example:

<?php

namespace AppTest;

class Sky
{
    public function __construct(private readonly string $registration, private readonly Airline $airline)
    {
    }

    public function getRegistration(): string
    {
        return $this->registration;
    }

    public function getAirline(): Airline
    {
        return $this->airline;
    }
}

And i have errors like:

Method should either have body or be abstract
Using '$this' when not in object context

But when i change constructor to this:

    public function __construct(string $registration,Airline $airline)
    {
    }

then i don’t have errors, does someone knows to explain why? because i think there is some problem that im not aware of