Example #1 Basic limited values
<?php
enum SortOrder
{
case Asc;
case Desc;
}
function query($fields, $filter, SortOrder $order = SortOrder::Asc)
{
/* ... */
}
?>
The query() function can now proceed safe in the knowledge that
$order is guaranteed to be either SortOrder::Asc
or SortOrder::Desc. Any other value would have resulted in a
TypeError , so no further error checking or testing is needed.
Example #2 Advanced exclusive values
<?php
enum UserStatus: string
{
case Pending = 'P';
case Active = 'A';
case Suspended = 'S';
case CanceledByUser = 'C';
public function label(): string
{
return match($this) {
self::Pending => 'Pending',
self::Active => 'Active',
self::Suspended => 'Suspended',
self::CanceledByUser => 'Canceled by user',
};
}
}
?>
In this example, a user's status may be one of, and exclusively, UserStatus::Pending,
UserStatus::Active, UserStatus::Suspended, or
UserStatus::CanceledByUser. A function can type a parameter against
UserStatus and then only accept those four values, period.
All four values have a label() method, which returns a human-readable string.
That string is independent of the "machine name" scalar equivalent string, which can be used in,
for example, a database field or an HTML select box.
<?php
foreach (UserStatus::cases() as $case) {
printf('<option value="%s">%s</option>\n', $case->value, $case->label());
}
?>Additional use-case examples:
<?php
trait EnumNamesTrait
{
abstract public static function cases(): array;
public static function names(): array
{
return array_map(fn($enum) => $enum->name, static::cases());
}
}
trait EnumValuesTrait
{
abstract public static function cases(): array;
public static function values(): array
{
return array_map(fn($enum) => $enum->value, static::cases());
}
}
trait EnumArraySerializableTrait
{
use EnumNamesTrait;
use EnumValuesTrait;
public static function array(): array
{
return array_combine(static::names(), static::values());
}
}
trait EnumJsonSerializableTrait
{
use EnumArraySerializableTrait;
public static function jsonSerialize(): string
{
return json_encode(static::array());
}
}
enum Suit: string
{
case Clubs = '♣';
case Diamonds = '♦';
case Hearts = '♥';
case Spades = '♠';
use EnumJsonSerializableTrait;
public const DEFAULT = self::Hearts;
public static function default(): static
{
return self::DEFAULT;
}
}
var_dump(
Suit::cases(),
Suit::values(),
Suit::names(),
Suit::array(),
Suit::jsonSerialize(),
Suit::default(),
);