Should interfaces be named with Interface suffix? And abstract classes with Abstract prefix?

Let’s think for a while — where do we use class/interface name?

• During creating object from the class (new Product(...))
• In usage

Creating objects

We aren’t able to create objects from abstract classes and interfaces, so it is always without prefix/suffix. I hope no one suggest to call a concrete class a new ClassProduct(...), but rather new Product(...).

OOP

I’d like to introduce a philosophical note here. What is object-oriented programming about? I believe that OOP is about

Encapsulating data by behavior.

Behavior means we use methods of objects, not their properties.

Usage

Let’s consider following code

class CartItem {
    private string $productId;
    private int $amount;
    public function price(Prices $prices): Price {
        $unitPrice = $prices->unitPrice($this->productId);
        return $unitPrice->multiply($this->amount);
    }
}

What is the Prices? Is it a class? Is it an abstract class? Is it an interface?

We don’t know.

And we don’t care!

The only think we care is

• What it represents? It represents prices.
• What method it provides? It provides unit price by a product ID.

Would the readability improve if we added prefix/suffix?

public function price(PricesInterface $prices): Price {
public function price(AbstractPrices $prices): Price {

I don’t see a value in such naming. The original variant is simpler and easier to read.

public function price(Prices $prices): Price {

Conclusion

When we use a certain concept, we care only about WHAT it represents and WHAT methods it provide. We don’t care whether it is a class, abstract class or interface.

Therefore I suggest to not use prefixes/suffixes for interfaces and abstract classes.

I suggest to spend more time on good naming instead.