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Examples

Example #1 Basic limited values

<?php
enum SortOrder
{
    case 
ASC;
    case 
DESC;
}

function 
query($fields$filterSortOrder $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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