Enums
Learn to define and use type-safe constants with enum.
Type-safe constants with enum
PHP 8.1 introduced enum to define a fixed set of values in a type-safe way. A Suit enum can list card suit names; it makes invalid values impossible.
Each case represents one value and stands for a singleton instance. Suit::Heart always returns the same object.
A parameter typed as Suit accepts only the four valid values; anything else fails at compile time or runtime.
Backed enum and enum methods
An enum can carry an int or string backed value: enum Status: int { case Active = 1; }. The int here is a scalar type; with PHP 8.0 union types parameters can also take combined types like int|string.
Backed enums expose Status::Active->value to read the value and Status::from(1) to build a case from a value.
An enum can also hold methods; a match expression inside picks behavior per case, so logic stays bound to state.
Exercise Suit backed enum
Define a string backed enum called Suit. Cases: Heart = "H", Diamond = "D", Club = "C", Spade = "S".
The echo line below should print H.
Show example solution
enum Suit: string {
case Heart = "H";
case Diamond = "D";
case Club = "C";
case Spade = "S";
}
echo Suit::Heart->value;Test yourself
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Complete the enum case
enum Suit { case Heart; case Diamond; case ____; case Spade; }Show answer
enum Suit { case Heart; case Diamond; case Club; case Spade; } -
What does Status::Active->value return?
enum Status: int { case Active = 1; case Paused = 2; }- Active
- 1
- Status
- true
Show answer
1 — Correct. Since the Active case is backed by 1, ->value returns 1.
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Match the enum concepts
- enum
- typed constant set
- case
- enum member
- backed
- value-carrying enum
- ->value
- access backed value