Update README.md

Author: Petr Knap

README.md

@@ -2,25 +2,85 @@
 
 Enumerated type for PHP by [Petr Knap].
 
+* [What is Enum?](#what-is-enum)
+* [Why use Enums instead of Constants?](#why-use-enums-instead-of-constants)
+* [Usage of php-enum](#usage-of-php-enum)
+    * [Enum declaration](#enum-declaration)
+    * [Enum usage](#enum-usage)
+* [How to install](#how-to-install)
 
-## 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.
+## 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
+## Why use Enums instead of Constants?
+
+Because **it is safer and less scary** than using constants. Don't trust me? Let see at this code:
+
+```php
+class MyBoolean
+{
+    const MY_TRUE = 1;
+    const MY_FALSE = 2;
+}
+
+function isTrue(int $myBoolean)
+{
+    switch($myBoolean) {
+        case MyBoolean::MY_TRUE:
+            return true;
+        case MyBoolean::MY_FALSE:
+            return false;
+    }
+}
+
+isTrue(MyBoolean::MY_TRUE);  // returns true - OK
+isTrue(MyBoolean::MY_FALSE); // returns false - OK
+isTrue(1);                   // returns true - OK
+isTrue(2);                   // returns false - scary, but OK
+isTrue(true);                // returns true - OK
+isTrue(false);               // returns null - WTF?
+```
+
+And now the **same code with Enum** instead of Constants:
+
+```php
+class MyBoolean extends \PetrKnap\Php\Enum\AbstractEnum
+{
+    protected function members()
+    {
+        return [
+            "MY_TRUE" => 1,
+            "MY_FALSE" => 2
+        ];
+    }
+}
+
+function isTrue(MyBoolean $myBoolean)
+{
+    switch($myBoolean) {
+        case MyBoolean::MY_TRUE():
+            return true;
+        case MyBoolean::MY_FALSE():
+            return false;
+    }
+}
+
+isTrue(MyBoolean::MY_TRUE());  // returns true - OK
+isTrue(MyBoolean::MY_FALSE()); // returns false - OK
+isTrue(1);                     // uncaught type error - OK
+isTrue(2);                     // uncaught type error - OK
+isTrue(true);                  // uncaught type error - OK
+isTrue(false);                 // uncaught type error - OK
+```
+
+
+## Usage of php-enum
 
-#### Enum declaration
+### 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 members()
@@ -38,7 +98,7 @@ class DayOfWeekEnum extends \PetrKnap\Php\Enum\AbstractEnum
 }
 ```
 
-#### Enum usage
+### Enum usage
 ```php
 if (DayOfWeekEnum::FRIDAY() == DayOfWeekEnum::FRIDAY()) {
     echo "This is OK.";
@@ -52,17 +112,15 @@ if (DayOfWeekEnum::FRIDAY() == DayOfWeekEnum::MONDAY()) {
 ```
 
 ```php
-switch($dayOfWeek)
+function isWeekend(DayOfWeekEnum $dayOfWeek)
 {
-    case DayOfWeekEnum::FRIDAY():
-        echo "Finally it is Friday!";
-        break;
-    case DayOfWeekEnum::SATURDAY():
-    case DayOfWeekEnum::SUNDAY():
-        echo "It is leasure time!";
-        break;
-    default:
-        echo "Just another working day...";
+   switch ($dayOfWeek) {
+       case DayOfWeekEnum::SATURDAY():
+       case DayOfWeekEnum::SUNDAY():
+           return true;
+       default:
+           return false;
+   }
 }
 ```