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Enum ####

Emulated enumeration objects in PHP.

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

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

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; }

Custom key-value source

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

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:

Output:

bool(true)
bool(true)

Ensuring existence of keys and values

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

See Error handling.

Getting keys for values or values for keys

Keys and values can be looked up using their counterpart:

Output:

int(4)
string(6) "FRIDAY"

Getting key/value lists and maps

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:

Output:

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

Counting members

Output:

int(7)

EnumObject

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

Defining an enum object class

/* @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'; }

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

var_dump($color);

Output:

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

Using a key

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.

var_dump($color);

Output:

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

Getting all instances

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

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

Output:

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

Getting the pair

var_dump($color->pair());

Output:

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

Comparing the key and value

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):

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)

Examples

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