Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

<?php
interface Renderable
{
    public function render(): string;
}

interface Cacheable
{
    public function getCacheKey(): string;
    public function getTtl(): int;
}

interface Loggable
{
    public function getLogContext(): array;
}

// A class can implement multiple interfaces
class HtmlWidget implements Renderable, Cacheable, Loggable
{
    public function __construct(
        private string $id,
        private string $content
    ) {}

public function render(): string
    {
        return "<div id=\"{$this->id}\">{$this->content}</div>";
    }

public function getCacheKey(): string
    {
        return "widget:{$this->id}";
    }

public function getTtl(): int { return 3600; }

public function getLogContext(): array
    {
        return ['widget_id' => $this->id, 'type' => static::class];
    }
}

// Type-hint against the interface, not the concrete class
function renderAll(Renderable ...$items): string
{
    return implode("
", array_map(fn($i) => $i->render(), $items));
}

$widget = new HtmlWidget('hero', 'Welcome!');
echo $widget->render();
echo ($widget instanceof Renderable) ? 'Renderable' : '';
echo ($widget instanceof Cacheable)  ? 'Cacheable'  : '';