Functional-ish generic Result type: either Success or Error




Library representing a generic Result type with Success and Error states, made for aiding this functional programming pattern in PHP.

It is generically typed using Psalm annotations, so you are expected to use Psalm if you want typechecking of your code.

Why using this library if graham-campbell/result-type exists?
Unfortunately, there are several downsides of that library:

  • while it's also typed with Psalm annotations, actually using and checking against them might be painful.
  • it's coupled to the phpoption/phpoption library which unfortunately suffers from the same problem.
  • there is no convenience method in Result interface which would allow getting either value from it.


This library requires PHP 7.4 or 8.0. You can install it via Composer:

composer install someniatko/result-type


See ResultInterface for details.



use Someniatko\ResultType\Success;
use Someniatko\ResultType\Error;

$value = (new Success('Let it be'))
    ->map(fn (string $s) => substr_count($s, ' ')) // Success<2>
    ->chain(fn (int $wordsCount) => $wordsCount > 3 
        ? new Success('Long text') 
        : new Error('short text')
    ) // Error<'short text'>
    ->map(fn (string $s) => str_replace(' ', '', $s)) // will not be called because we're in Error result
    ->mapError(fn (string $s) => strtoupper($s)) // Error<'SHORT TEXT'>
    ->get(); // 'SHORT TEXT'