Code

Step 1: Activate RESTful Webservice

Active modules:

HAL (hal)

RESTful Web Services (rest)    

HTTP Basic Authentication (basic_auth)

Download and active contrib modules:

REST UI (restui)

You can call drupal 8 services statically as D7, but it is not the best practice (Like Here).

Example : $uuid = \Drupal::service('uuid')->generate();

Create a Service on Drupal 8

1.  Create a custom module (here : mytest)

2. Create the service Class

Example: src/MTService.php

Get All available services list

$services = \Drupal::getContainer()->getServiceIds();

Few use full services

//Generate a new UUID

$uuid = \Drupal::service('uuid')->generate();

Once created your entity as Basic Entity or Full Entity, you can add a custom views handler.

This is a full Example of the Entity 'Vehicle' with user interfaces for:

- Actions (Create, Edit, Delete)

- Listing builder

- Entity settings pages

   - Manage fields

   - Manage form display

   - Manage display

Drupal 8 has two type of entities, ContentEntity and ConfigEntity. Content entity is based on database table and config entity is based on Drupal config table.

Standard weights:

medium -> font-weight : 500;

semi-bold ->font-weight : 600;

Font Face

Example

Basic php and drupal 7 / 8 Examples

1.

$string_out = html_entity_decode($string, ENT_QUOTES, 'UTF-8')

//Do not forget ENT_QUOTES and 'UTF-8', otherwise quotes will not decodes.

Drupal Utility list

ArgumentsResolver, ArgumentsResolverInterface, Bytes, Color, Crypt, DiffArray, Environment, Html, Image, NestedArray, Number, OpCodeCache, Random, Rectangle, SafeMarkup, SortArray, Tags, Timer, ToStringTrait, Unicode, UrlHelper, UserAgent, Variable, Xss