TH\Maybe

This library implements two monadic types for PHP :

Option

Type Option represents an optional value: every Option is either Option\Some and contains a value, or Option\None, and does not

Result

Result is the type used for returning and propagating errors. It has two variants, Ok(T), representing success and containing a value, and Err(E), representing error and containing an error value.

Using those types makes it easier to handle result of operations correctly. Those two types are also carefully annotated to help static analysis tools discover potential issues such as invalid returned type or dead code.

Installation

composer req texthtml/maybe

Basic usages

Using Options

use TH\Maybe\Option;

/**
 * @param Option<float>
 */
function divide(float $numerator, float $denominator): Option {
    return match ($denomintor) {
        0.0 => Option\none(),
        _ => Option\some($numerator / $denominator)
    };
}

// The return value of the function is an option
$result = divide(2.0, 3.0);

// Pattern match to retrieve the value
if ($result instanceof Option\Some) {
    // The division was valid
    echo "Result: {$option->unwrap()}");
} else {
    // The division was invalid
    echo "Cannot divide by 0";
}

Read more about Options

Using Results

use TH\Maybe\Option;

/**
 * @param Result<int,string>
 */
function parse_version(string $header): Result {
    return match ($header[0] ?? null) {
        null => Result\err("invalid header length"),
        "1" => Result\ok(1),
        "2" => Result\ok(2),
        default => Result\err("invalid version"),
    };
}

$version = parse_version("1.x");
if ($version instanceof Result\Ok) {
    echo "working with version: {$version->unwrap()}";
} else {
    echo "error parsing header: {$version->unwrapErr()}";
}
// @prints working with version: 1

Read more about Results