Basic Algorithms for PHP

PHP's built-in functions such as array_map, array_filter and array_reduce have a few issues:

• They only work with arrays
• They are eager instead of lazy
• They are cumbersome to compose

This repository provides definitions for common algorithms such as map, filter, and reduce with certain characteristics:

• They work with any type that can be used in a foreach loop
• They are lazy
• They are not (too) cumbersome to compose

Building

PHP does not have function autoloading at the time of this writing. Since this project is mostly functions it uses a makefile to build load.php which will include all of the functions for use. You can also build a phar or run the unit tests:

• make (or make load.php): builds load.php
• make phar: builds morrisonlevi_algorithm.phar
• make check: runs the phpunit test suite

There is a script registered in the composer.json that will build load.php if the composer autoloader gets built.

Examples

This example does a basic map. Note that the function that does the mapping comes first and the input data comes second:

<?php

namespace morrisonlevi\Algorithm;

require __DIR__ . '/load.php';

$mul2 = function ($value) {
    return $value * 2;
};

$result = map($mul2)([1,2,3]);

var_export(iterator_to_array($result));
/*
array (
  0 => 2,
  1 => 4,
  2 => 6,
)
*/

This example chains a filter, map and sum together:

<?php

namespace morrisonlevi\Algorithm;

require __DIR__ . '/load.php';

$odd = function($value) {
   return $value % 2 > 0;
};

$mul2 = function($value) {
    return $value * 2;
};

$algorithm = chain(
    filter($odd),
    map($mul2),
    sum()
);

var_dump($algorithm([1,2,3])); // int(8)