Phprelude

The standard library I wish PHP always had.

Significant credit belongs to leocavalcante/Siler, whose Functional library has been largely transplanted into this project, and who, in addition, has made programming in PHP bearable for me and other FP zealots.

Usage

Composer

Install via

composer install "samuelludwig/phprelude"

And then autoload the library namespaces via the typical

require_once __DIR__ . '/path/to/vendor/autoload.php';

Manual Install + Require

If you opt to add the library as a submodule to your project, you can conveniently require all files in the library by using the autoload.php file a la

require_once __DIR__ . '/path/to/Phprelude/autoload.php';

Modules

The modules breakdown as follows:

• Core: Suitable primatives for FP tools
• Enum: Functions for processing and manipulating "Enumerables" (Arrays)
• Io: Functions for I/O
• Math: Math-related functions
• Natural: Integer-related functions
• Str: String-related functions
• File: File-related functions
• Environment: Environment-variable-related functions
• Json: JSON-related functions

Notable Features

Piping!

Users of Elixirs wonderful |> operator or the threading macro -> found in most lisps should be very familar with the concept of this function.

Graciously taken verbatim from Siler is the indespensible pipe. Few things make my eyes glaze over as much as nested function calls and intermediate variables: this is where Core\pipe comes to the rescue!

We can supply pipe with a list of callbacks which each expect one argument, and as a result we will receive a lambda, which will feed the output of each callback into the next one in the list, and finally returning the output of the last callback.

Here's an example:

<?php declare(strict_types=1); namespace StructTest;
require_once __DIR__ . '\path\to\Phprelude\autoload.php';
use \Phprelude\Core as p;
use Closure;

function add2($n) {
  return $n+2;
}

function ladd2(): Closure {
  return fn($x) => add2($x);
}

$double = fn($n) => $n*2;
$triple = fn($n) => $n*3;

echo p\pipe([
  $triple,
  $double,
  fn($x) => add2($x),
  ladd2(),
])(4); // (4 * 3 * 2) + 2 + 2 ==> 28

Pipelines are a blessing when it comes to data-transformation/processing, never need to create an intermediate variable ever again!

Just about every function in this library should have an accompanying lambda-ized version (oft named l<original-funcs-name>) to make piping more immediately convienient.

Extraction and Manipulation

Extracting values into a given format

The Enum module houses a myriad of tools dedicated to manipulating data housed in arrays.

One of my personal highest-milage functions when it comes to picking out and molding data is easily Enum\extract_values_into_format.

This function accepts two values, a source array, to extract from, and a mapping of new key-names to keys in the source array. A map of new-key to source-key may also involve a transformation of source-key's value; in which case, source-key will be given as an array, the first element being the key name, and the second being the callable to apply to the value.

So,

<?php declare(strict_types=1); namespace StructTest;
require_once __DIR__ . '\path\to\Phprelude\autoload.php';
use \Phprelude\Enum;
use Closure;

// Say I have an array like
$a = [ 'pets_name' => 'mark', 'pet_kind' => 'dog' ];
// and I have some function thats expecting the keys to be named differently, like
// "`animal_name`" instead of "`pet_name`" and "`species`" instead of "`pet_kind`",
// and maybe its also expecting the `species` to always be capitalized, I could
// then write

$new_a =
  Enum\extract_values_into_format(
    $a,
    [ 'animal_name' => 'pets_name'
    , 'species' => ['pet_kind', fn($x) => strtoupper($x)]
    ]);

// Et voila, we have our new array
echo $new_a == [ 'animal_name' => 'mark', 'species' => 'DOG' ]; // 1

A similar, more narrowly-focused version of this function exists called Enum\extract_values, which will merely return list of the requested values. My main use case for this function is destructuring some select fields I care about explicitly:

<?php declare(strict_types=1); namespace StructTest;
require_once __DIR__ . '\path\to\Phprelude\autoload.php';
use \Phprelude\Enum;
use Closure;

// Given:
$a = [ 'first' => 'door', 'second' => 'cat', 'third' => 'orange' ];

// We can extract specific values into a list via:
[ $x, $y ] = Enum\extract_values($a, ['third', 'first']);

echo "$x $y"; // "orange door"

Comparing against contents of an array

TODO: is_true_for_all/some_elements

Structs!? In my PHP!?

One of the most recent (read: unrefined) new additions to this library is the abuse of PHP constants to create a naive implementation of structs, with a pseudo-built-in general constructor function.

A struct is defined using the Core\defstruct function, which takes two arguments:

1. The name of the struct
2. The "layout" of the struct

A struct's layout is an associative array, with each key being the name of a given field, and each value being a one or two element array, where the first element is either:

1. Another nested struct layout
2. A list of possible "types" the ultimate value can be, either the core types understood by PHP, or names of other structs

The second element, if there is one, will be the default value for a given field if one was not provided in the constructor function.

When a struct is defined using defstruct, a constant, named using the provided name of the struct, is created and set to the value of the structs layout. Note that this means defstruct is impure, because you will be adding constants to the global namespace!

After declaration, a struct can be constructed using the Core\mk function, which takes the name of the struct, and an associative array. Fields with defined defaults, that are not also present in the provided associative array, are substituted with their given default values. The mk function will error if the resulting array does not match the type of the struct.

NOTE: At the moment, a struct, after definition, can have a superset of the fields in its layout, and still be considered the same "type".

An example struct definition (and subsequent construction) might look like:

<?php declare(strict_types=1); namespace StructTest;
require_once __DIR__ . '\path\to\Phprelude\autoload.php';
use \Phprelude\Core as p;
use \Phprelude\Json;

// We can use const to pseudo-namespace our struct without too much hassle
const UserT = __NAMESPACE__ . '\User';
p\defstruct(
    UserT,
    [ 'id' => [['int', 'string'], 0]
    , 'name' => [['string']]
    ]);

$user0 = p\mk(UserT, ['name' => 'John']);
$user1 = p\mk(UserT, ['id' => 1, 'name' => 'Mike']);

echo Json\encode($user0) . "\n"; // {"id":0,"name":"John"}
echo Json\encode($user1) . "\n"; // {"id":1,"name":"Mike"}

Wants and Desires

• Type aliases, i.e. non-struct type definitions, ex: Num = ['int','float']
• Add ability to use guard clauses with type definitions, for example, some way to write BigNat = int > 1000 (Type "BigNat" corresponds to an int with a value greater than 1000)
• Clean up overall implementation of structs+types
• Add a "strict" version of type-checking for structs, which doesn't accept extra fields that aren't in the initial struct