<?php

// abstract class
abstract class Greetings 
{        
    // abstract method
    abstract public function greet(string $name) : string;
    
    // regular method
    public function bye(string $name) : string {
        return "Bye, $name\n";
    }
}

// extend abstract class
class Main extends Greetings 
{
    // implement abstract method
    public function greet(string $name) : string {
        return "Hello, $name!\n";
    }
}

$g = new Main();
echo $g->greet("Jake");
echo $g->bye("Jake");