PHP Enum implementation inspired from SplEnum

Why?

First, and mainly, SplEnum is not integrated to PHP, you have to install the extension separately.

Using an enum instead of class constants provides the following advantages:

You can use an enum as a parameter type: function setAction(Action $action) {
You can use an enum as a return type: function getAction() : Action {
You can enrich the enum with methods (e.g. format, parse, …)
You can extend the enum to add new values (make your enum final to prevent it)
You can get a list of all the possible values (see below)

This Enum class is not intended to replace class constants, but only to be used when it makes sense.

composer require gusarov112/php-enum

use Gusarov112\Enum\Enum;

/**
 * Action enum
 */
class Action extends Enum
{
    private const VIEW = 'view';
    private const EDIT = 'edit';
}

$action = new Action(Action::VIEW);

One advantage over using class constants is to be able to use an enum as a parameter type:

function setAction(Action $action) {
    // ...
}

__construct() The constructor checks that the value exist in the enum
__toString() You can echo $myValue, it will display the enum value (value of the constant)
getValue() Returns the current value of the enum
getKey() Returns the key of the current value on Enum
equals() Tests whether enum instances are equal (returns true if enum values are equal, false otherwise)

Static methods:

toArray() method Returns all possible values as an array (constant name in key, constant value in value)
keys() Returns the names (keys) of all constants in the Enum class
values() Returns instances of the Enum class of all Enum constants (constant name in key, Enum instance in value)
isValid() Check if tested value is valid on enum set
isValidKey() Check if tested key is valid on enum set
search() Return key for searched value