Esempi

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) {
static::
Pending => 'Pending',
static::
Active => 'Active',
static::
Suspended => 'Suspended',
static::
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:
<?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(),
);
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