PHP Enumerations (Enums)
Enumerations, or Enums, allow a developer to define a custom type that is limited to a discrete set of possible values. They are useful when you have a variable that can only take one of a small set of possible values.
Enums were introduced in PHP 8.1.
Basic Enums
A basic enum is a type that has a fixed number of possible values.
<?php
enum Status {
case DRAFT;
case PUBLISHED;
case ARCHIVED;
}
function setStatus(Status $status) {
// ...
}
setStatus(Status::DRAFT);
?>In the example above, the Status enum can only be Status::DRAFT, Status::PUBLISHED, or Status::ARCHIVED. The setStatus function is guaranteed to receive one of these values.
Backed Enums
Backed enums are enums that are "backed" by a scalar value (either an int or a string). This is useful for storing the enum value in a database or other storage.
<?php
enum Status: string {
case DRAFT = 'draft';
case PUBLISHED = 'published';
case ARCHIVED = 'archived';
}
echo Status::PUBLISHED->value; // 'published'
$status = Status::from('published'); // Status::PUBLISHED
$status = Status::tryFrom('unknown'); // null
?>Key features of Backed Enums:
- They must declare a scalar type (
intorstring). - All cases must have a unique scalar equivalent.
from()method: returns the Enum case corresponding to a scalar value. Throws aValueErrorif the value is not found.tryFrom()method: returns the Enum case ornullif the value is not found.
Enums with Methods
Enums can also have methods, making them even more powerful.
<?php
enum Status: string {
case DRAFT = 'draft';
case PUBLISHED = 'published';
case ARCHIVED = 'archived';
public function label(): string {
return match($this) {
self::DRAFT => 'Draft',
self::PUBLISHED => 'Published',
self::ARCHIVED => 'Archived',
};
}
}
echo Status::PUBLISHED->label(); // 'Published'
?>