php_8/interfaces/topic.php

<?php
require_once 'image_cover.php';

class Topic implements Cover
{
    private $path;

    public function __construct(
        public string $title,
        public string $content,
        public ?int $published_at = null)
    {
        if (empty($published_at)) {
            $this->published_at = time();
        } else {
            $this->published_at = $published_at;
        }
    }
    public function getImage() : string
    {
        return $this->path;
    }
    public function setImage(string $path) : void
    {
        $this->path = $path;
    }
}