PHP OOP Abstract Interface Inheritance Factory Pattern Magic method

gistfile1.php

<?php
/**
 * common things about a developer
 */
abstract class Developer {
    protected $_languages;
    protected $_characteristics;

    abstract public function setLanguages($language);
    abstract public function getLanguages();
    abstract public function setCharacteristics($characteristics);
    abstract public function getCharacteristics();
    abstract public function display();
}

/**
 * Extra things that a developer / others might want to do
 */
interface Others {
    public function doTravel();
}

/**
 * Web developer
 */
class WebDeveloper extends Developer implements Others {
    public $doTravel = FALSE;
    protected $_activities = [];
    protected $_name = 'Anonymous';

    public function __construct($name = NULL) {
        if($name) $this->_name = $name;
    }

    public function __toString() {
        return $this->display();
    }

    public static function set($name) {
        return new self($name);
    }
    
    public function setLanguages($language = []) {
        $this->_languages = $language;
        return $this;
    }
    
    public function getLanguages() {
        return $this->_languages;
    }
    
    public function setCharacteristics($characteristics = []) {
        $this->_characteristics = $characteristics;
        return $this;
    }
    
    public function getCharacteristics() {
        return $this->_characteristics;
    }

    public function setActivities($activity = []) {
        $this->_activities = $activity;
        return $this;
    }

    public function getActivities($activity = []) {
        return $this->_activities;
    }

    public function display() {
        return json_encode([
            'name' => $this->_name,
            'know' => $this->getLanguages(),
            'is' => $this->getCharacteristics(),
            'activities' => $this->getActivities(),
        ]);
    }

    public function doTravel() {
        return $this->doTravel;
    }

}

$me = WebDeveloper::set('Habib Hadi');
$me->setLanguages(['JavaScript', 'PHP'])
    ->setCharacteristics(['Self constructed', 'Creative', 'Curious'])
    ->setActivities(['Watch Game of Thrones', 'Like Heisenberg', 'Play Sniper Ghost Warrior']);
echo $me;