Update README.md

Author: Petr Knap

README.md

@@ -1,2 +1,69 @@
 # php-enum
-Enumerated type for PHP
+
+Enumerated type for PHP by [Petr Knap].
+
+
+## What is enum?
+
+> In computer programming, an **enumerated type** (also called **enumeration** or **enum**, or **factor** in the R programming language, and a categorical variable in statistics) is a data type consisting of a set of named values called **elements**, **members**, **enumeral**, or **enumerators** of the type. The enumerator names are usually identifiers that behave as constants in the language. A variable that has been declared as having an enumerated type can be assigned any of the enumerators as a value. In other words, an *enumerated type has values that are different from each other*, and that can be compared and assigned, but which are not specified by the programmer as having any particular concrete representation in the computer's memory; compilers and interpreters can represent them arbitrarily.
+-- [Enumerated type - Wikipedia, The Free Encyclopedia]
+
+### Usage of php-enum
+
+#### Enum declaration
+```php
+/**
+ * @method static DayOfWeekEnum SUNDAY()
+ * @method static DayOfWeekEnum MONDAY()
+ * @method static DayOfWeekEnum TUESDAY()
+ * @method static DayOfWeekEnum WEDNESDAY()
+ * @method static DayOfWeekEnum THURSDAY()
+ * @method static DayOfWeekEnum FRIDAY()
+ * @method static DayOfWeekEnum SATURDAY()
+ */
+class DayOfWeekEnum extends \PetrKnap\Php\Enum\AbstractEnum
+{
+    protected function __construct($constantName)
+    {
+        self::setConstants([
+            "SUNDAY" => 0,
+            "MONDAY" => 1,
+            "TUESDAY" => 2,
+            "WEDNESDAY" => 3,
+            "THURSDAY" => 4,
+            "FRIDAY" => 5,
+            "SATURDAY" => 6
+        ]);
+        parent::__construct($constantName);
+    }
+}
+```
+
+#### Enum usage
+```php
+if (date('w') == DayOfWeekEnum::FRIDAY()->getValue()) {
+    echo "Finally it is Friday!";
+}
+```
+
+
+## How to install
+
+Run `composer require petrknap/php-enum` or merge this JSON code with your project `composer.json` file manually and run `composer install`. Instead of `dev-master` you can use [one of released versions].
+
+```json
+{
+    "require": {
+        "petrknap/php-enum": "dev-master"
+    }
+}
+```
+
+Or manually clone this repository via `git clone https://github.com/petrknap/php-enum.git` or download [this repository as ZIP] and extract files into your project.
+
+
+
+[Petr Knap]:http://petrknap.cz/
+[Enumerated type - Wikipedia, The Free Encyclopedia]:https://en.wikipedia.org/w/index.php?title=Enumerated_type&oldid=701057934
+[one of released versions]:https://github.com/petrknap/php-enum/releases
+[this repository as ZIP]:https://github.com/petrknap/php-enum/archive/master.zip