endtoend-test-psl/README.md

# Psl - PHP Standard Library

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Psl is a standard library for PHP, inspired by [hhvm/hsl](https://github.com/hhvm/hsl).

The goal of Psl is to provide a consistent, centralized, well-typed set of APIs for PHP programmers.

## Example
```php
<?php

declare(strict_types=1);

use Psl\Str;
use Psl\Iter;

/**
 * @psalm-param iterable<?int> $codes
 */
function foo(iterable $codes): string
{
    /** @var Iter\Iterator<int> $codes */
    $codes = Iter\filter_nulls($codes);
    /** @var Iter\Iterator<string> $chars */
    $chars = Iter\map($codes, fn(int $code): string => Str\chr($code));

    return Str\join($chars, ', ');
}

foo([95, 96, null, 98]);
// 'a, b, d'
```

## Installation

This package doesn't have a stable release yet, but you can still install it using composer :

```console
$ composer require azjezz/psl:dev-develop
```

## Documentation

Documentation is not available yet.

## Principles

 - All functions should be typed as strictly as possible
 - The library should be internally consistent
 - References may not be used
 - Arguments should be as general as possible. For example, for `array` functions, prefer `iterable` inputs where practical, falling back to `array` when needed.
 - Return types should be as specific as possible
 - All files should contain `declare(strict_types=1);`

## Consistency Rules

This is not exhaustive list.

 - Functions argument order should be consistent within the library
   - All iterable-related functions take the iterable as the first argument ( e.g. `Iter\map` and `Iter\filter` )
   - `$haystack`, `$needle`, and `$pattern` are in the same order for all functions that take them
 - Functions should be consistently named.
 - If an operation can conceivably operate on either keys or values, the default is to operate on the values - the version that operates on keys should have `_key` suffix (e.g. `Iter\last`, `Iter\last_key`, `Iter\contains`, `Iter\contains_key` )
 - Find-like operations that can fail should return `?T`; a second function should be added with an `x` suffix that uses an invariant to return `T` (e.g. `Arr\last`, `Arr\lastx`)
 - Iterable functions that do an operation based on a user-supplied keying function for each element should be suffixed with `_by` (e.g. `Arr\sort_by`, `Iter\group_by`, `Math\max_by`)

## License

The MIT License (MIT). Please see [`LICENSE`](./LICENSE) for more information.