Enum

Emulated enumeration objects in PHP.

The interface is similar to SplEnum but doesn't require any PHP extensions and provides more functionality.

Contents

• Features
• Requirements
• Usage
  • Enum
    • Defining an enum class
      • Custom key-value source
    • Supported value types
    • Method overview
      • Checking keys and values
      • Ensuring existence of keys and values
      • Getting keys for values or values for keys
      • Getting key/value lists and maps
      • Getting pairs
      • Counting members
  • EnumObject
    • Defining an enum object class
    • Creating instances
      • Using a value
      • Using a key
      • Using the magic static factory method
      • Getting all instances
    • Method overview
      • Getting the key and value
      • Getting the pair
      • Comparing the key and value
      • String conversion
  • Error handling
  • Value type coercion
    • Examples

Features

• immutability
• ensured unique keys and values
• simple to use (just extend a class and define some class constants)
• many methods related to keys
• values and their enumeration, maps and checking
• enum instances
• detailed exception messages

Requirements

• PHP 7.1+

Usage

Enum

The static Enum class provides access to the defined key-value pairs.

Defining an enum class

<?php

use Kuria\Enum\Enum;

abstract class DayOfTheWeek extends Enum
{
    const MONDAY = 0;
    const TUESDAY = 1;
    const WEDNESDAY = 2;
    const THURSDAY = 3;
    const FRIDAY = 4;
    const SATURDAY = 5;
    const SUNDAY = 6;
}

Note

Private and protected constants are ignored.

Custom key-value source

To define key-value pairs using some other source than class constants, override the static determineKeyToValueMap() method:

<?php

use Kuria\Enum\Enum;

abstract class Example extends Enum
{
   protected static function determineKeyToValueMap(): array
   {
        return [
            'FOO' => 'bar',
            'BAZ' => 'qux',
            'QUUX' => 'quuz',
        ];
   }
}

Supported value types

Only string, integer and null values are supported.

Values must be unique when used as an array key. See Value type coercion.

Values are looked up and compared with the same type-coercion rules as PHP array keys. See Value type coercion.

Method overview

Checking keys and values

Verify the existence of a key or a value:

<?php

var_dump(
    DayOfTheWeek::hasKey('MONDAY'),
    DayOfTheWeek::hasValue(0)
);

Output:

bool(true)
bool(true)

Ensuring existence of keys and values

Make sure a key or a value exists, otherwise throw an exception:

<?php

DayOfTheWeek::ensureKey('MONDAY');
DayOfTheWeek::ensureValue(0);

See Error handling.

Getting keys for values or values for keys

Keys and values can be looked up using their counterpart:

<?php

var_dump(
    DayOfTheWeek::getValue('FRIDAY'),
    DayOfTheWeek::getKey(4)
);

Output:

int(4)
string(6) "FRIDAY"

Note

If the key or value doesn't exist, an exception will be thrown. See Error handling.

To get NULL instead of an exception, use the findValue() or findKey() method instead.

Getting key/value lists and maps

<?php

echo 'DayOfTheWeek::getKeys(): '; print_r(DayOfTheWeek::getKeys());
echo 'DayOfTheWeek::getValues(): '; print_r(DayOfTheWeek::getValues());
echo 'DayOfTheWeek::getMap(): '; print_r(DayOfTheWeek::getMap());
echo 'DayOfTheWeek::getKeyMap(): '; print_r(DayOfTheWeek::getKeyMap());
echo 'DayOfTheWeek::getValueMap(): '; print_r(DayOfTheWeek::getValueMap());

Output:

DayOfTheWeek::getKeys(): Array
(
    [0] => MONDAY
    [1] => TUESDAY
    [2] => WEDNESDAY
    [3] => THURSDAY
    [4] => FRIDAY
    [5] => SATURDAY
    [6] => SUNDAY
)
DayOfTheWeek::getValues(): Array
(
    [0] => 0
    [1] => 1
    [2] => 2
    [3] => 3
    [4] => 4
    [5] => 5
    [6] => 6
)
DayOfTheWeek::getMap(): Array
(
    [MONDAY] => 0
    [TUESDAY] => 1
    [WEDNESDAY] => 2
    [THURSDAY] => 3
    [FRIDAY] => 4
    [SATURDAY] => 5
    [SUNDAY] => 6
)
DayOfTheWeek::getKeyMap(): Array
(
    [MONDAY] => 1
    [TUESDAY] => 1
    [WEDNESDAY] => 1
    [THURSDAY] => 1
    [FRIDAY] => 1
    [SATURDAY] => 1
    [SUNDAY] => 1
)
DayOfTheWeek::getValueMap(): Array
(
    [0] => MONDAY
    [1] => TUESDAY
    [2] => WEDNESDAY
    [3] => THURSDAY
    [4] => FRIDAY
    [5] => SATURDAY
    [6] => SUNDAY
)

Getting pairs

A pair is an array with a single key and the corresponding value. They can be retrieved using either the key or the value:

<?php

var_dump(DayOfTheWeek::getPair(DayOfTheWeek::MONDAY));
var_dump(DayOfTheWeek::getPairByKey('FRIDAY'));

Output:

array(1) {
  ["MONDAY"]=>
  int(0)
}
array(1) {
  ["FRIDAY"]=>
  int(4)
}

Counting members

<?php

var_dump(DayOfTheWeek::count());

Output:

int(7)

EnumObject

The EnumObject class extends from Enum and adds factory methods to create instances.

Defining an enum object class

<?php

use Kuria\Enum\EnumObject;

/**
 * @method static static RED()
 * @method static static GREEN()
 * @method static static BLUE()
 */
class Color extends EnumObject
{
    const RED = 'r';
    const GREEN = 'g';
    const BLUE = 'b';
}

Note

The @method annotations are not required, but they will aid in code-completion and inspection.

See Magic static factory methods.

Creating instances

Instances can be created by one of the factory methods. Those instances are cached internally and reused, so that multiple calls to the factory methods with the same key or value will yield the same instance.

Enum instances cannot be cloned.

Using a value

<?php

$color = Color::fromValue(Color::RED);

var_dump($color);

Output:

object(Foo\Color)#5 (2) {
  ["key"]=>
  string(3) "RED"
  ["value"]=>
  string(1) "r"
}

Using a key

<?php

$color = Color::fromKey('GREEN');

var_dump($color);

Output:

object(Foo\Color)#3 (2) {
  ["key"]=>
  string(5) "GREEN"
  ["value"]=>
  string(1) "g"
}

Using the magic static factory method

For every key there is a static method with the same name, which returns an instance for that key-value pair.

<?php

$color = Color::BLUE();

var_dump($color);

Output:

object(Foo\Color)#5 (2) {
  ["key"]=>
  string(4) "BLUE"
  ["value"]=>
  string(1) "b"
}

Warning

Magic static factory method names are case-sensitive.

Getting all instances

<?php

var_dump(Color::all());

Output:

array(3) {
  ["RED"]=>
  object(Foo\Color)#5 (2) {
    ["key"]=>
    string(3) "RED"
    ["value"]=>
    string(1) "r"
  }
  ["GREEN"]=>
  object(Foo\Color)#4 (2) {
    ["key"]=>
    string(5) "GREEN"
    ["value"]=>
    string(1) "g"
  }
  ["BLUE"]=>
  object(Foo\Color)#2 (2) {
    ["key"]=>
    string(4) "BLUE"
    ["value"]=>
    string(1) "b"
  }
}

Method overview

Getting the key and value

<?php

$color = Color::RED();

var_dump(
    $color->key(),
    $color->value()
);

Output:

string(3) "RED"
string(1) "r"

Getting the pair

<?php

$color = Color::GREEN();

var_dump($color->pair());

Output:

array(1) {
  ["GREEN"]=>
  string(1) "g"
}

Comparing the key and value

<?php

 $color = Color::RED();

 var_dump(
     $color->is('RED'),   // compare key
     $color->is('GREEN'), // compare key
     $color->equals('r'), // compare value
     $color->equals('g')  // compare value
 );

Output:

bool(true)
bool(false)
bool(true)
bool(false)

String conversion

Converting an instance to a string will yield its value (cast to a string):

<?php

$color = Color::BLUE();

echo $color;

Output:

b

Error handling

Most error states are handled by throwing an exception.

All exceptions thrown by the enum classes implement Kuria\Enum\Exception\ExceptionInterface.

• Kuria\Enum\Exception\InvalidKeyException is thrown when a key doesn't exist
• Kuria\Enum\Exception\InvalidValueException is thrown when a value doesn't exist
• Kuria\Enum\Exception\InvalidMethodException is thrown when a magic factory method doesn't exist
• Kuria\Enum\Exception\DuplicateValueException is thrown when an enum class defines duplicate values

Value type coercion

Values are looked up and compared with the same type-coercion rules as PHP array keys. See PHP manual for a detailed explanation.

With string, integer and null being the supported value types, this means that the following values are equal:

• null and "" (an empty string)
• 123 and "123" (a numeric string)

Note

The public API, e.g. Enum::getValue() and EnumObject::value(), always returns the value as defined by the enum class.

Note

Array key type coercion is NOT the same as loose comparison (==).

Examples

<?php

use Kuria\Enum\EnumObject;

class IntAndNullEnum extends EnumObject
{
    const INT_KEY = 123;
    const NULL_KEY = null;
}

class StringEnum extends EnumObject
{
    const NUMERIC_STRING_KEY = '123';
    const EMPTY_STRING_KEY = '';
}

// value checks
var_dump(
    IntAndNullEnum::hasValue('123'),
    IntAndNullEnum::hasValue('0123'),
    IntAndNullEnum::hasValue(''),
    IntAndNullEnum::hasValue(' '),
    StringEnum::hasValue(123),
    StringEnum::hasValue('0123'),
    StringEnum::hasValue(null),
    StringEnum::hasValue(' ')
);

// value retrieval
var_dump(
    (IntAndNullEnum::fromValue('123'))->value(),
    (IntAndNullEnum::fromValue(''))->value(),
    (StringEnum::fromValue(123))->value(),
    (StringEnum::fromValue(null))->value()
);

Output for value checks:

bool(true)    // '123' matches 123
bool(false)   // '0123' does not match 123
bool(true)    // '' matches NULL
bool(false)   // ' ' does not match NULL
bool(true)    // 123 matches '123'
bool(false)   // '0123' does not match '123'
bool(true)    // NULL matches ''
bool(false)   // ' ' does not match ''

Output for value retrieval:

int(123)          // enum created with '123' but 123 is returned
NULL              // enum created with '' but NULL is returned
string(3) "123"   // enum created with 123 but '123' is returned
string(0) ""      // enum created with NULL but '' is returned