Override-Default.php

<?php
interface Formatter {
    public function format(string $input): string;
}

trait DefaultFormatter {
    #[\Override]
    public function format(string $input): string {
        // Default formatter simply returns the input as is.
        return $input; 
    }
}

class CustomFormatter {
    // Using trait to provide a default implementation.
    use DefaultFormatter; 
}