marc-mabe/php-enum

Simple and fast implementation of enumerations with native PHP 5.3 and upper

v2.2.1 2016-09-06 14:41 UTC

README

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This is a native PHP implementation to add enumeration support to PHP >= 5.3. It's an abstract class that needs to be extended to use it.

What is an Enumeration?

Wikipedia

In computer programming, an enumerated type (also called enumeration or enum) is a data type consisting of a set of named values called elements, members 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 do not have any particular concrete representation in the computer's memory; compilers and interpreters can represent them arbitrarily.

Usage

PHPDoc

You can find auto-generated PHP documentation in the wiki.

Basics

use MabeEnum\Enum;

// define an own enumeration class
class UserStatus extends Enum
{
    const INACTIVE = 0;
    const ACTIVE   = 1;
    const DELETED  = 2;

    // all scalar datatypes are supported
    const NIL     = null;
    const BOOLEAN = true;
    const INT     = 1234;
    const STR     = 'string';
    const FLOAT   = 0.123;

    // Arrays are supported since PHP-5.6
    const ARR = array('this', 'is', array('an', 'array'));

    // Enumerators will be generated from public constants only
    public    const PUBLIC_CONST    = 'public constant';    // this will be an enumerator
    protected const PROTECTED_CONST = 'protected constant'; // this will NOT be an enumerator
    private   const PRIVATE_CONST   = 'private constant';   // this will NOT be an enumerator

    // works since PHP-7.0 - see https://wiki.php.net/rfc/context_sensitive_lexer
    const TRUE      = true;
    const FALSE     = false;
    const NULL      = null;
    const PUBLIC    = 'public';
    const PRIVATE   = 'private';
    const PROTECTED = 'protected';
    const FUNCTION  = 'function';
    const TRAIT     = 'trait';
    const INTERFACE = 'interface';

    // Doesn't work - see https://wiki.php.net/rfc/class_name_scalars
    // const CLASS = 'class';
}

// different ways to instantiate an enumerator
$status = UserStatus::get(UserStatus::ACTIVE);
$status = UserStatus::ACTIVE();
$status = UserStatus::getByName('ACTIVE');
$status = UserStatus::getByOrdinal(1);

// available methods to get the selected entry
$status->getValue();   // returns the selected constant value
$status->getName();    // returns the selected constant name
$status->getOrdinal(); // returns the ordinal number of the selected constant
(string) $status;      // returns the selected constant name

// same enumerators (of the same enumeration class) holds the same instance
UserStatus::get(UserStatus::ACTIVE) === UserStatus::ACTIVE()
UserStatus::get(UserStatus::DELETED) != UserStatus::INACTIVE()

// simplified way to compare two enumerators
$status = UserStatus::ACTIVE();
$status->is(UserStatus::ACTIVE);     // true
$status->is(UserStatus::ACTIVE());   // true
$status->is(UserStatus::DELETED);    // false
$status->is(UserStatus::DELETED());  // false

Type-Hint

use MabeEnum\Enum;

class User
{
    protected $status;

    public function setStatus(UserStatus $status)
    {
        $this->status = $status;
    }

    public function getStatus()
    {
        if (!$this->status) {
            // initialize the default enumerator
            $this->status = UserStatus::get(UserStatus::INACTIVE);
        }
        return $this->status;
    }
}

Type-Hint issue

Because in normal OOP the above example allows UserStatus and types inherited from it.

Please think about the following example:

class ExtendedUserStatus
{
    const EXTENDED = 'extended';
}

$user->setStatus(ExtendedUserStatus::EXTENDED());

Now the setter receives a status it doesn't know about but allows it. If your User class doesn't allow it the following is the recommanded way:

class User
{
    // ...
    public function setStatus($status)
    {
        $this->status = UserStatus::get($status);
    }
    // ...
}

Now you are 100% sure to work with an exact instance of UserStatus.

If the setter receives an ExtendedUserStatus an exception will be thrown because inheritance is not allowed with Enum::get.

On the same time this method will accept scalar values matching one of the defined values of UserStatus and returns an instance of it.

EnumSet

An EnumSet groups enumerators of the same enumeration type together.

It implements Iterator and Countable so it's simple to iterate the set or count all attached enumerators of it with foreach and count().

Internally it's based on a bitset of a binary string so the order will be by the ordinal number by design.

use MabeEnum\EnumSet;

// create a new EnumSet
$enumSet = new EnumSet('UserStatus');

// attach enumerators (by value or by instance)
$enumSet->attach(UserStatus::INACTIVE);
$enumSet->attach(UserStatus::ACTIVE());
$enumSet->attach(UserStatus::DELETED());

// detach enumerators (by value or by instance)
$enumSet->detach(UserStatus::INACTIVE);
$enumSet->detach(UserStatus::DELETED());

// contains enumerators (by value or by instance)
$enumSet->contains(UserStatus::INACTIVE); // bool

// count number of attached enumerations
$enumSet->count();
count($enumSet);

// convert to array
$enumSet->getValues();      // List of enumerator values
$enumSet->getEnumerators(); // List of enumerator instances
$enumSet->getNames();       // List of enumerator names
$enumSet->getOrdinals();    // List of ordinal numbers

// compare two EnumSets
$enumSet->isEqual($other);    // Check if the EnumSet is the same as other
$enumSet->isSubset($other);   // Check if the EnumSet is a subset of other
$enumSet->isSuperset($other); // Check if the EnumSet is a superset of other

$enumSet->union($other[, ...]);     // Produce a new set with enumerators from both this and other (this | other)
$enumSet->intersect($other[, ...]); // Produce a new set with enumerators common to both this and other (this & other)
$enumSet->diff($other[, ...]);      // Produce a new set with enumerators in this but not in other (this - other)
$enumSet->symDiff($other[, ...]);   // Produce a new set with enumerators in either this and other but not in both (this ^ (other | other))

EnumMap

An EnumMap maps enumerators of the same type to data assigned to.

Internally an EnumMap is based of SplObjectStorage.

use MabeEnum\EnumMap;

// create a new EnumMap
$enumMap = new EnumMap('UserStatus');

// attach entries (by value or by instance)
$enumMap->attach(UserStatus::INACTIVE, 'inaktiv');
$enumMap->attach(UserStatus::ACTIVE(), 'aktiv');
$enumMap->attach(UserStatus::DELETED(), 'gelöscht');

// detach entries (by value or by instance)
$enumMap->detach(UserStatus::INACTIVE);
$enumMap->detach(UserStatus::DELETED());

// iterate
var_dump(iterator_to_array($enumMap)); // array(0 => UserStatus{$value=1});

// define key and value used for iteration
$enumMap->setFlags(EnumMap::KEY_AS_NAME | EnumMap::CURRENT_AS_DATA);
var_dump(iterator_to_array($enumMap)); // array('ACTIVE' => 'aktiv');

Serializing

Because this enumeration implementation is based on a singleton pattern and in PHP it's currently impossible to unserialize a singleton without creating a new instance this feature isn't supported without any additional work.

As of it's an often requested feature there is a trait that can be added to your enumeration definition. The trait adds serialization functionallity and injects the unserialized enumeration instance in case it's the first one. This reduces singleton behavior breakage but still it beaks if it's not the first instance and you could result in two different instance of the same enumeration.

Use it with caution!

Example of using EnumSerializableTrait

use MabeEnum\Enum;
use MabeEnum\EnumSerializableTrait;
use Serializable;

class CardinalDirection extends Enum implements Serializable
{
    use EnumSerializableTrait;

    const NORTH = 'n';
    const EAST  = 'e';
    const WEST  = 'w';
    const SOUTH = 's';
}

$north1 = CardinalDirection::NORTH();
$north2 = unserialize(serialize($north1));

// The following could be FALSE as described above
var_dump($north1 === $north2);

Why not SplEnum

  • SplEnum is not build-in into PHP and requires pecl extension installed.
  • Instances of the same value of an SplEnum are not the same instance.
  • SplEnum doesn't have implemented EnumMap or EnumSet.

Install

Composer

Add marc-mabe/php-enum to the project's composer.json dependencies and run php composer.phar install

GIT

git clone git://github.com/marc-mabe/php-enum.git

ZIP / TAR

Download the last version from Github and extract it.

New BSD License

The files in this archive are released under the New BSD License. You can find a copy of this license in LICENSE.txt file.