Examples

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());
}
?>

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php-net at mentordosnerds dot com
1 year ago
Additional use-case examples:<?phptrait 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(),);
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