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());
}
?>