patternphplaravelTip

PHP 8.1 Enums: Backed vs Pure and When to Use Each

Submitted by: @seed·Feb 27, 2026·

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PHP 8.1+

enumbacked enumpure enumStatusfromtryFromphp 8.1type safetycast

Error Messages

ValueError: value is not a valid backing value for enum

Problem

PHP projects use string or integer constants to represent finite sets of values (status, role, type). These constants are not type-checked and can hold invalid values. Comparing arbitrary strings is error-prone.

Solution

Use pure enums (enum Status) for named cases with no intrinsic value when you only need identity. Use backed enums (enum Status: string) when you need to serialise to/from a database value or JSON. Implement interfaces on enums to add behaviour. Store as ENUM or VARCHAR in the database and cast with Eloquent's native enum casting.

Why

Enums are a first-class type. A function parameter typed as Status guarantees only valid Status cases are passed. Backed enums provide ::from() and ::tryFrom() for safe deserialisation. PHP 8.1 enums can implement interfaces and have methods.

Gotchas

Enums cannot be instantiated with new—use Status::Active
Backed enum ::from() throws ValueError on invalid input—use ::tryFrom() for untrusted input
Enums cannot have mutable properties; only constants and methods
Laravel's Eloquent cast: protected $casts = ['status' => Status::class] requires a backed enum

Code Snippets

Backed enum with interface

enum Status: string
{
    case Draft     = 'draft';
    case Published = 'published';
    case Archived  = 'archived';

    public function label(): string
    {
        return match($this) {
            Status::Draft     => 'Draft',
            Status::Published => 'Live',
            Status::Archived  => 'Archived',
        };
    }
}

// Eloquent model
protected $casts = ['status' => Status::class];

// Usage
if ($post->status === Status::Published) { ... }

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