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) {
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());
}
?>