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PHP Enum implementation inspired from SplEnum

Why?

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

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

You can type-hint: function setAction(Action $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.

Installation

composer require myclabs/php-enum

Declaration

use MyCLabs\Enum\Enum;

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

Note the private keyword requires PHP > 7.1, you can omit it on PHP 7.0.

Usage

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

// or
$action = Action::VIEW();

As you can see, static methods are automatically implemented to provide quick access to an enum value.

One advantage over using class constants is to be able to type-hint enum values:

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

Documentation

__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

Static methods

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

// Static method:
$action = Action::VIEW();
$action = Action::EDIT();

Static method helpers are implemented using __callStatic().

If you care about IDE autocompletion, you can either implement the static methods yourself:

class Action extends Enum
{
    private const VIEW = 'view';

    /**
     * @return Action
     */
    public static function VIEW() {
        return new Action(self::VIEW);
    }
}

or you can use phpdoc (this is supported in PhpStorm for example):

/**
 * @method static Action VIEW()
 * @method static Action EDIT()
 */
class Action extends Enum
{
    private const VIEW = 'view';
    private const EDIT = 'edit';
}

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