### Install Result Type with Composer

Source: https://github.com/grahamcampbell/result-type/blob/1.1/README.md

Use this command to add the latest version of the Result Type package to your project. Ensure you are using PHP 7.2.5 or higher.

```bash
$ composer require "graham-campbell/result-type:^1.1"
```

--------------------------------

### Access Results with success() and error() using Option wrappers

Source: https://context7.com/grahamcampbell/result-type/llms.txt

The `success()` and `error()` methods return `PhpOption\Option` instances, providing safe value access without null checks. Use `getOrElse()` for safe retrieval with a fallback value, or `get()` for direct retrieval which throws an exception if the Option is empty.

```php
<?php

use GrahamCampbell\ResultType\Success;
use GrahamCampbell\ResultType\Error;

$ok  = Success::create(99);
$err = Error::create('oops');

// isDefined() / isEmpty()
var_dump($ok->success()->isDefined());  // bool(true)
var_dump($ok->error()->isEmpty());      // bool(true)
var_dump($err->error()->isDefined());   // bool(true)
var_dump($err->success()->isEmpty());   // bool(true)

// getOrElse() — safe retrieval with fallback
$value = $ok->success()->getOrElse(0);   // 99
$value = $err->success()->getOrElse(0);  // 0

// get() — direct retrieval (throws RuntimeException if None)
$value = $ok->success()->get();  // 99
// $err->success()->get() would throw: "None has no value."

// orElse() — return an alternative Option
$fallback = $err->success()->orElse(\PhpOption\Some::create(-1));
echo $fallback->get(); // -1
```

--------------------------------

### Create Error Result

Source: https://context7.com/grahamcampbell/result-type/llms.txt

Wrap an error value using `Error::create()`. The `error()` accessor returns `Some($value)` and `success()` returns `None`. Attempting `get()` on the `None` side will throw a `RuntimeException`.

```php
<?php

use GrahamCampbell\ResultType\Error;

// Wrap a validation or domain error
$result = Error::create('User not found');

var_dump($result->error()->isDefined());   // bool(true)
var_dump($result->success()->isEmpty());   // bool(true)

$message = $result->error()->get(); // 'User not found'

// Safely read error with fallback — never throws
$message = $result->error()->getOrElse('Unknown error');

// Attempting ->get() on the None side throws RuntimeException
try {
    $result->success()->get();
} catch (\RuntimeException $e) {
    echo $e->getMessage(); // "None has no value."
}

```

--------------------------------

### Create Success Result

Source: https://context7.com/grahamcampbell/result-type/llms.txt

Wrap a successful value using `Success::create()`. The `success()` accessor returns `Some($value)` and `error()` returns `None`. Safe retrieval with `getOrElse()` is recommended.

```php
<?php

use GrahamCampbell\ResultType\Success;

// Wrap a successful database lookup result
$result = Success::create(['id' => 42, 'name' => 'Alice']);

// Check and retrieve success value
$successOption = $result->success(); // PhpOption\Some
$errorOption   = $result->error();   // PhpOption\None

var_dump($successOption->isDefined()); // bool(true)
var_dump($errorOption->isEmpty());     // bool(true)

$user = $successOption->get(); // ['id' => 42, 'name' => 'Alice']

// Safe retrieval with a fallback (never throws)
$user = $result->success()->getOrElse([]);

```

--------------------------------

### Result::success() and Result::error()

Source: https://context7.com/grahamcampbell/result-type/llms.txt

Access Option wrappers for success and error values. Both methods return a PhpOption\Option instance. `success()` returns `Some(value)` on a `Success` and `None` on an `Error`; `error()` is the inverse. The `Option` API provides safe value access without null checks.

```APIDOC
## `Result::success()` and `Result::error()` — Access Option wrappers

Both methods return a `PhpOption\Option` instance. `success()` returns `Some(value)` on a `Success` and `None` on an `Error`; `error()` is the inverse. The `Option` API provides safe value access without null checks.

```php
<?php

use GrahamCampbell\ResultType\Success;
use GrahamCampbell\ResultType\Error;

$ok  = Success::create(99);
$err = Error::create('oops');

// isDefined() / isEmpty()
var_dump($ok->success()->isDefined());  // bool(true)
var_dump($ok->error()->isEmpty());      // bool(true)
var_dump($err->error()->isDefined());   // bool(true)
var_dump($err->success()->isEmpty());   // bool(true)

// getOrElse() — safe retrieval with fallback
$value = $ok->success()->getOrElse(0);   // 99
$value = $err->success()->getOrElse(0);  // 0

// get() — direct retrieval (throws RuntimeException if None)
$value = $ok->success()->get();  // 99
// $err->success()->get() would throw: "None has no value."

// orElse() — return an alternative Option
$fallback = $err->success()->orElse(\PhpOption\Some::create(-1));
echo $fallback->get(); // -1
```
```

--------------------------------

### Success::create($value)

Source: https://context7.com/grahamcampbell/result-type/llms.txt

Creates a Result instance representing a successful outcome, wrapping any value. The success() accessor returns Some($value) and error() returns None.

```APIDOC
## Success::create($value) - Wrap a successful value

### Description
Creates a `Result` instance representing a successful outcome, wrapping any value of type `T`. The `success()` accessor returns `Some($value)` and `error()` returns `None`.

### Method
`Success::create($value)`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```php
<?php

use GrahamCampbell\ResultType\Success;

// Wrap a successful database lookup result
$result = Success::create(['id' => 42, 'name' => 'Alice']);

// Check and retrieve success value
$successOption = $result->success(); // PhpOption\Some
$errorOption   = $result->error();   // PhpOption\None

var_dump($successOption->isDefined()); // bool(true)
var_dump($errorOption->isEmpty());     // bool(true)

$user = $successOption->get(); // ['id' => 42, 'name' => 'Alice']

// Safe retrieval with a fallback (never throws)
$user = $result->success()->getOrElse([]);
```

### Response
#### Success Response (200)
None

#### Response Example
None
```

--------------------------------

### Chain Result-Returning Operations with flatMap

Source: https://context7.com/grahamcampbell/result-type/llms.txt

Use `flatMap` to chain operations that return a `Result`. The callable is skipped if the initial `Result` is an `Error`, and the error propagates. This method is useful for building pipelines of operations that may fail.

```php
<?php

use GrahamCampbell\ResultType\Success;
use GrahamCampbell\ResultType\Error;
use GrahamCampbell\ResultType\Result;

function parsePositiveInt(string $input): Result {
    return is_numeric($input) && (int)$input > 0
        ? Success::create((int)$input)
        : Error::create("'{$input}' is not a positive integer");
}

function divide(int $numerator, int $denominator): Result {
    return $denominator !== 0
        ? Success::create($numerator / $denominator)
        : Error::create('Division by zero');
}

// Chain: parse input, then divide
$result = parsePositiveInt('100')
    ->flatMap(fn(int $n) => divide(200, $n));

echo $result->success()->get(); // 2

// Short-circuits on first failure
$result = parsePositiveInt('abc')
    ->flatMap(fn(int $n) => divide(200, $n));

echo $result->error()->get(); // "'abc' is not a positive integer"

// flatMap returning Error mid-chain
$result = Success::create('foo')
    ->flatMap(fn(string $s) => Error::create('OH NO'));

echo $result->error()->get(); // 'OH NO'
```

--------------------------------

### Error::create($value)

Source: https://context7.com/grahamcampbell/result-type/llms.txt

Creates a Result instance representing a failed outcome, wrapping any error value. The error() accessor returns Some($value) and success() returns None.

```APIDOC
## Error::create($value) - Wrap an error value

### Description
Creates a `Result` instance representing a failed outcome, wrapping any error value of type `E`. The `error()` accessor returns `Some($value)` and `success()` returns `None`.

### Method
`Error::create($value)`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```php
<?php

use GrahamCampbell\ResultType\Error;

// Wrap a validation or domain error
$result = Error::create('User not found');

var_dump($result->error()->isDefined());   // bool(true)
var_dump($result->success()->isEmpty());   // bool(true)

$message = $result->error()->get(); // 'User not found'

// Safely read error with fallback — never throws
$message = $result->error()->getOrElse('Unknown error');

// Attempting ->get() on the None side throws RuntimeException
try {
    $result->success()->get();
} catch (\RuntimeException $e) {
    echo $e->getMessage(); // "None has no value."
}
```

### Response
#### Success Response (200)
None

#### Response Example
None
```

--------------------------------

### Transform Success Value with map()

Source: https://context7.com/grahamcampbell/result-type/llms.txt

Use `map()` to apply a callable to the success value, returning a new `Success`. When called on an `Error`, `map()` is a no-op and the original error is returned.

```php
<?php

use GrahamCampbell\ResultType\Success;
use GrahamCampbell\ResultType\Error;

// Transform success: uppercase a string value
$result = Success::create('hello')->map('strtoupper');
echo $result->success()->get(); // 'HELLO'

// map() on an Error is a no-op — error passes through
$result = Error::create('something went wrong')->map('strtoupper');
echo $result->error()->get(); // 'something went wrong'

// Practical example: parse and transform an API response
function fetchUsername(int $id): Result {
    // Simulate a lookup
    return $id > 0
        ? Success::create('alice')
        : Error::create('Invalid ID');
}

$display = fetchUsername(1)
    ->map(fn(string $name) => strtoupper($name))  // 'ALICE'
    ->map(fn(string $name) => "Welcome, {$name}!"); // 'Welcome, ALICE!'

echo $display->success()->getOrElse('Error occurred'); // 'Welcome, ALICE!'

```

--------------------------------

### Result::flatMap(callable $f)

Source: https://context7.com/grahamcampbell/result-type/llms.txt

Applies a callable to the success value where the callable itself returns a Result. This enables safe chaining of operations that may themselves fail, without nesting. When called on an Error, the callable is skipped and the original error propagates.

```APIDOC
## `Result::flatMap(callable $f)` — Chain result-returning operations

Applies a callable to the success value where the callable itself returns a `Result`. This enables safe chaining of operations that may themselves fail, without nesting. When called on an `Error`, the callable is skipped and the original error propagates.

```php
<?php

use GrahamCampbell\ResultType\Success;
use GrahamCampbell\ResultType\Error;
use GrahamCampbell\ResultType\Result;

function parsePositiveInt(string $input): Result {
    return is_numeric($input) && (int)$input > 0
        ? Success::create((int)$input)
        : Error::create("'{$input}' is not a positive integer");
}

function divide(int $numerator, int $denominator): Result {
    return $denominator !== 0
        ? Success::create($numerator / $denominator)
        : Error::create('Division by zero');
}

// Chain: parse input, then divide
$result = parsePositiveInt('100')
    ->flatMap(fn(int $n) => divide(200, $n));

echo $result->success()->get(); // 2

// Short-circuits on first failure
$result = parsePositiveInt('abc')
    ->flatMap(fn(int $n) => divide(200, $n));

echo $result->error()->get(); // "'abc' is not a positive integer"

// flatMap returning Error mid-chain
$result = Success::create('foo')
    ->flatMap(fn(string $s) => Error::create('OH NO'));

echo $result->error()->get(); // 'OH NO'
```
```

--------------------------------

### Result::map(callable $f)

Source: https://context7.com/grahamcampbell/result-type/llms.txt

Applies a callable to the wrapped success value and returns a new Success. If called on an Error, the callable is ignored and the original error is returned.

```APIDOC
## Result::map(callable $f) - Transform a success value

### Description
Applies a callable to the wrapped success value and returns a new `Success` wrapping the transformed result. When called on an `Error`, the callable is ignored and the original error is returned unchanged.

### Method
`Result::map(callable $f)`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```php
<?php

use GrahamCampbell\ResultType\Success;
use GrahamCampbell\ResultType\Error;

// Transform success: uppercase a string value
$result = Success::create('hello')->map('strtoupper');
echo $result->success()->get(); // 'HELLO'

// map() on an Error is a no-op — error passes through
$result = Error::create('something went wrong')->map('strtoupper');
echo $result->error()->get(); // 'something went wrong'

// Practical example: parse and transform an API response
function fetchUsername(int $id): Result {
    // Simulate a lookup
    return $id > 0
        ? Success::create('alice')
        : Error::create('Invalid ID');
}

$display = fetchUsername(1)
    ->map(fn(string $name) => strtoupper($name))  // 'ALICE'
    ->map(fn(string $name) => "Welcome, {$name}!"); // 'Welcome, ALICE!'

echo $display->success()->getOrElse('Error occurred'); // 'Welcome, ALICE!'
```

### Response
#### Success Response (200)
None

#### Response Example
None
```

--------------------------------

### Result::mapError(callable $f)

Source: https://context7.com/grahamcampbell/result-type/llms.txt

Applies a callable to the wrapped error value and returns a new Error. If called on a Success, the callable is ignored and the original success is returned.

```APIDOC
## Result::mapError(callable $f) - Transform an error value

### Description
Applies a callable to the wrapped error value and returns a new `Error` wrapping the transformed result. When called on a `Success`, the callable is ignored and the original success is returned unchanged.

### Method
`Result::mapError(callable $f)`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```php
<?php

use GrahamCampbell\ResultType\Success;
use GrahamCampbell\ResultType\Error;

// Transform error: normalize error message formatting
$result = Error::create('not found')->mapError('ucfirst');
echo $result->error()->get(); // 'Not found'

// mapError() on a Success is a no-op
$result = Success::create('data')->mapError('strtoupper');
echo $result->success()->get(); // 'data'

// Practical example: enrich error with context
$result = Error::create('connection refused')
    ->mapError(fn(string $msg) => "[DB Error] {$msg}");

echo $result->error()->get(); // '[DB Error] connection refused'
```

### Response
#### Success Response (200)
None

#### Response Example
None
```

--------------------------------

### Transform Error Value with mapError()

Source: https://context7.com/grahamcampbell/result-type/llms.txt

Use `mapError()` to apply a callable to the error value, returning a new `Error`. When called on a `Success`, `mapError()` is a no-op and the original success is returned.

```php
<?php

use GrahamCampbell\ResultType\Success;
use GrahamCampbell\ResultType\Error;

// Transform error: normalize error message formatting
$result = Error::create('not found')->mapError('ucfirst');
echo $result->error()->get(); // 'Not found'

// mapError() on a Success is a no-op
$result = Success::create('data')->mapError('strtoupper');
echo $result->success()->get(); // 'data'

// Practical example: enrich error with context
$result = Error::create('connection refused')
    ->mapError(fn(string $msg) => "[DB Error] {$msg}");

echo $result->error()->get(); // '[DB Error] connection refused'

```

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