gistfile1.php

<?php
// Interface
inferface ArchiveElement {
    public function do_something();   
}

class TC_Video implements ArchiveElement {
    public function do_something() {
        // does something
    }
}

// Abstract
abstract class ArchiveElement {
    abstract public function do_something();
    
    protected function do_something_else() {
        // ... do something else
    }
}

class TC_Video extends ArchiveElement {
    public function do_something() {
        // does something
        
        $this->do_something_else();
    }
}