How to use Enum in PHP 8

Enums are one of the basic features of many programming languages, and PHP is no exception. Here's everything you need to know about Enums in PHP .

Enumeration (enum) is a data type that you can use to store a value from a custom set. They're perfect for representing the type of options you can show in a drop-down list.

PHP 8.1 now supports enums. Using enums is easy but they provide additional features borrowed from object-oriented programming.

Effects of Enum

Enums are useful when you want to work with a fixed set of related values. For example, you can use an enum to represent sets in a card pack or media type.

PHP's enums are quite complex, with some features borrowed from classes. You can use them in combination with type hints to write more predictable and rigorous code.

Basic enums

Enums typically store scalar values. They are similar to C's primitive data types, although PHP enums can contain string values ​​as well as integers. However, by default, PHP enum values ​​do not have scalar equivalents. These are called basic enums:

enum Season {     case Spring;     case Summer;     case Autumn;     case Winter; }

Note how PHP reuses the case keyword, which you'll encounter in the switch statement. What the enum values ​​represent are just the names of the instances. You can refer to a specific enum value with the following command:

EnumTypeName::EnumField

For example, to refer to winter, use:

Season::Winter

You can assign this value to a variable and test it against other Season values:

$favorite = Season::Summer;   if ($favorite == get_current_season()) {     echo "It's my favorite season!"; }

Using type hints, you can limit parameters or return types to a specific enum. This helps avoid a series of errors and makes editing the code easier:

function get_current_season(): Season {     $day = date("z");       if ($day < 59 || $day > 333) return Season::Winter;     if ($day < 151) return Season::Spring;     if ($day < 243) return Season::Summer;     if ($day < 334) return Season::Autumn; }

If the get_current_season function tries to return a value other than Season, PHP will raise a fatal TypeError.

Enums are supported

PHP uses the term 'backed enum' to refer to an enum with values. They can be integers or strings:

enum Month: int {     case Jan = 1;     case Feb = 2;     //. }

You need to declare the supported enum type and it must be int or string. You can access the underlying value using the read-only value property :

echo Month::Jan->value;

When using supported enums, you can also convert them, from their scalar equivalent, using the from method :

var_dump(Month::from(2));

enum methods

PHP enums also have methods, making them a bit like a shortened class. This shows PHP's position, between procedural and object-oriented languages.

For example, you can add this simple method to the Month enum to get the number of days from a specific value:

/* Note: no leap-year handling! */ function daysInMonth(): int {     if ($this == Month::Feb) return 28;     if (in_array($this, array(Month::Apr, Month::Jun, Month::Sep, Month::Nov))) return 30;     return 31; }

Note, you can use $this to refer to a specific enum value, just like you use $this to refer to a certain object. You can also use the standard equality operator, ==, to compare enum values.

Enum also supports static methods. For example:

static function random(): Month {     return Month::from(rand(1, count(Month::cases()))); }

Above are the things you need to know about enums in PHP . Hope this article is useful to you.

Jessica Tanner

Update 16 October 2023