Use of Interface, Abstract class and Inheritance example

OfferStatusCodeClass.php

<?php

namespace classes;

use interfaces\OfferStatusCode as interfaceOSC;

/**
 * Abstract class Offers Status Code
 *
 *
 * @see https://stackoverflow.com/questions/41611058/why-does-php-allow-abstract-static-functions
 * Luckily, the estimable Nikita Popov has removed the warning from the
 * language in PHP 7 as part of PHP RFC: Reclassify E_STRICT notices.
 * Ultimately, sanity has prevailed, and once PHP 7 is released we can all
 * happily use abstract static without receiving this silly warning.
 *
 */
abstract class AbstractOSC implements interfaceOSC {
  public static function getMessage($code = null) {
    $allMessages = static::getAllMessages();

    return isset($allMessages[$code])
      ? $allMessages[$code]
      : self::MSG_STATUS_DEFAULT;
  }

  abstract static function getAllMessages();
}

/**
 * Class for Generic offer status codes
 */
class OfferStatusCode extends AbstractOSC {
  public static function getAllMessages() {
    return [
      self::STATUS_DEFAULT => self::MSG_STATUS_DEFAULT,
      self::STATUS_0 => self::MSG_STATUS_0,
      self::STATUS_1 => self::MSG_STATUS_1,
      self::STATUS_2 => self::MSG_STATUS_2,
      self::STATUS_3 => self::MSG_STATUS_3,
      self::STATUS_4 => self::MSG_STATUS_4,
      self::STATUS_5 => self::MSG_STATUS_5,
      self::STATUS_6 => self::MSG_STATUS_6,
      self::STATUS_7 => self::MSG_STATUS_7,
      self::STATUS_8 => self::MSG_STATUS_8,
      self::STATUS_9 => self::MSG_STATUS_9,
      self::STATUS_11 => self::MSG_STATUS_11,
    ];
  }

}

/**
 * Class for Buyer offer status codes
 */
class BuyerOfferStatusCode extends OfferStatusCode {
  public static function getAllMessages() {
    $allMessages = parent::getAllMessages();

    $allMessages[self::STATUS_0] = self::MSG_STATUS_0 . ' given to seller.';
    $allMessages[self::STATUS_1] = self::MSG_STATUS_1 . ' by seller.';
    $allMessages[self::STATUS_2] = self::MSG_STATUS_2 . ' by seller.';
    $allMessages[self::STATUS_3] = self::MSG_STATUS_3 . ' by you.';
    $allMessages[self::STATUS_4] = self::MSG_STATUS_4 . ' received from seller.';
    $allMessages[self::STATUS_5] = self::MSG_STATUS_5 . ' given to seller.';
    $allMessages[self::STATUS_6] = self::MSG_STATUS_6 . ' by you.';
    $allMessages[self::STATUS_8] = self::MSG_STATUS_8 . ' from seller.';
    $allMessages[self::STATUS_9] = self::MSG_STATUS_9 . ' from seller, check with Domain Registrar.';

    return $allMessages;
  }
}

/**
 * Class for Seller offer status codes
 */
class SellerOfferStatusCode extends OfferStatusCode {
  public static function getAllMessages() {
    $allMessages = parent::getAllMessages();

    $allMessages[self::STATUS_0] = self::MSG_STATUS_0 . ' received from buyer.';
    $allMessages[self::STATUS_1] = self::MSG_STATUS_1 . ' by you.';
    $allMessages[self::STATUS_2] = self::MSG_STATUS_2 . ' by you.';
    $allMessages[self::STATUS_3] = self::MSG_STATUS_3 . ' by buyer.';
    $allMessages[self::STATUS_4] = self::MSG_STATUS_4 . ' given to buyer.';
    $allMessages[self::STATUS_5] = self::MSG_STATUS_5 . ' received from buyer.';
    $allMessages[self::STATUS_6] = self::MSG_STATUS_6 . ' by buyer.';
    $allMessages[self::STATUS_8] = 'Provide authorization code to buyer.';
    $allMessages[self::STATUS_9] = self::MSG_STATUS_9 . ' to buyer, awaiting confirmation.';

    return $allMessages;
  }
}

/**
 * Class for System offer status codes
 */
class SystemOfferStatusCode extends OfferStatusCode {
  public static function getAllMessages() {
    $allMessages = parent::getAllMessages();

    $allMessages[self::STATUS_1] = self::MSG_STATUS_1 . ' by seller.';
    $allMessages[self::STATUS_2] = self::MSG_STATUS_2 . ' by seller.';
    $allMessages[self::STATUS_3] = self::MSG_STATUS_3 . ' by buyer.';
    $allMessages[self::STATUS_4] = self::MSG_STATUS_4 . ' from seller.';
    $allMessages[self::STATUS_5] = self::MSG_STATUS_5 . ' from buyer.';
    $allMessages[self::STATUS_6] = self::MSG_STATUS_6 . ' by buyer.';
    $allMessages[self::STATUS_9] = self::MSG_STATUS_9 . ' from seller.';
    $allMessages[self::STATUS_11] = 'New offer expired.';

    return $allMessages;
  }
}

OfferStatusCodeInterface.php

<?php
interface OfferStatusCode {
  // Offer Status Codes
  const STATUS_DEFAULT = '-1';
  const STATUS_0 = '0';
  const STATUS_1 = '1';
  const STATUS_2 = '2';
  const STATUS_3 = '3';
  const STATUS_4 = '4';
  const STATUS_5 = '5';
  const STATUS_6 = '6';
  const STATUS_7 = '7';
  const STATUS_8 = '8';
  const STATUS_9 = '9';
  const STATUS_11 = '11';

  // Offer Status Messages
  const MSG_STATUS_DEFAULT = 'Unknown offer status';
  const MSG_STATUS_0 = 'New offer';
  const MSG_STATUS_1 = 'Offer accepted';
  const MSG_STATUS_2 = 'Offer canceled';
  const MSG_STATUS_3 = self::MSG_STATUS_2;
  const MSG_STATUS_4 = 'Counter offer';
  const MSG_STATUS_5 = self::MSG_STATUS_4;
  const MSG_STATUS_6 = self::MSG_STATUS_1;
  const MSG_STATUS_7 = 'Awaiting payment confirmation';
  const MSG_STATUS_8 = 'Awaiting authorization code';
  const MSG_STATUS_9 = 'Domain push';
  const MSG_STATUS_11 = 'Offer expired';


  public static function getMessage();
  public static function getAllMessages();
}