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Result object for PHP inspired by Rust
Branch: master
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A PHP implementation of Rust's Result type with roughly the same API.


composer require prewk/result


use Prewk\Result;
use Prewk\Result\{Ok, Err};

function someApiCall(): Result {
    // ...
    if ($apiCallSuccesful) {
        return new Ok($results);
    } else {
        return new Err($error);

function anotherApiCall(): Result {
    // ...
    if ($apiCallSuccesful) {
        return new Ok($results);
    } else {
        return new Err($error);

// Fallback to value
$value = someApiCall()->unwrapOr(null);

// Fallback to result and throw an exception if both fail
$value = someApiCall()->orElse(function($err) {
	return anotherApiCall();

// Throw custom exception on error
$value = someApiCall()->expect(new Exception("Oh noes!"));


Optional global helper functions exist to simplify result object construction:

ok(); // new Prewk\Result\Ok(null);
ok($val); // new Prewk\Result\Ok($val);
err($e); // new Prewk\Result\Err($e);

Add the following to your composer.json:

    "autoload": {
        "files": [

API deviations from Rust


If an Err containing an Exception is unwrapped, that Exception will be thrown. Otherwise a generic ResultException will be thrown.


If all results are Ok, give them to the contained callable value as arguments and put the callable's returned value in a new Ok. If any result is an Err, return the first Err.

$sum = function(int $foo, int $bar): int
	return $foo + bar;

ok($sum)->apply(ok(100), ok(200), ok(300)); // Ok<600>

ok($sum)->apply(ok(100), ok(200), err(new Exception)); // Err<Exception>


The with method will include the variadically added arguments in consecutive closures (map, andThen, etc). This is useful when chaining dependent ops.

ok($foo)->with($bar, $baz)
	->map(function($foo, $bar, $baz) {
		return $foo . $bar . $baz;


Note that or and and will be evaluated immediately:

// This will call all three api calls regardless of successes/errors

See andThen and orElse for lazy evaluation.


MIT & Apache 2.0

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