PHPNgrams

PHP N-Grams library

Introduction

In the fields of computational linguistics, machine-learning and probability, an n-gram is a contiguous sequence of n items from a given sample of text or speech. The items can be phonemes, syllables, letters, words or base pairs according to the application. The n-grams typically are collected from a text or speech corpus. When the items are words, n-grams may also be called shingles.

An n-gram of size 1 is referred to as a "unigram"; size 2 is a "bigram" (or, less commonly, a "digram"); size 3 is a "trigram". Larger sizes are sometimes referred to by the value of n in modern language, e.g., "four-gram", "five-gram", and so on. (More on Wikipedia)

Requirements

• PHP >= 7.0

Installation

Include this library in your project by doing:

composer require drupol/phpngrams

The library provides two classes:

• NGrams
• NGramsCyclic

and one trait:

• NGramsTrait

Usage

<?php

declare(strict_types = 1);

namespace drupol\phpngrams\tests;

use drupol\phpngrams\NGrams;
use drupol\phpngrams\NGramsCyclic;

include 'vendor/autoload.php';

$string = 'hello world';

// Better use preg_split() than str_split() in case of UTF8 strings.
$chars = preg_split('/(?!^)(?=.)/u', $string);

$ngrams = (new NGrams())->ngrams($chars, 3);

print_r(iterator_to_array($ngrams));
/*
[
    0 =>
        [
            0 => 'h',
            1 => 'e',
            2 => 'l',
        ],
    1 =>
        [
            0 => 'e',
            1 => 'l',
            2 => 'l',
        ],
    2 =>
        [
            0 => 'l',
            1 => 'l',
            2 => 'o',
        ],
    3 =>
        [
            0 => 'l',
            1 => 'o',
            2 => ' ',
        ],
    4 =>
        [
            0 => 'o',
            1 => ' ',
            2 => 'w',
        ],
    5 =>
        [
            0 => ' ',
            1 => 'w',
            2 => 'o',
        ],
    6 =>
        [
            0 => 'w',
            1 => 'o',
            2 => 'r',
        ],
    7 =>
        [
            0 => 'o',
            1 => 'r',
            2 => 'l',
        ],
    8 =>
        [
            0 => 'r',
            1 => 'l',
            2 => 'd',
        ],
];
*/

$string = 'hello world';

// Better use preg_split() than str_split() in case of UTF8 strings.
$chars = preg_split('/(?!^)(?=.)/u', $string);

$ngrams = (new NGramsCyclic())->ngrams($chars, 3);

print_r(iterator_to_array($ngrams));
/*
[
    0 => [
            0 => 'h',
            1 => 'e',
            2 => 'l',
        ],
    1 => [
            0 => 'e',
            1 => 'l',
            2 => 'l',
        ],
    2 => [
            0 => 'l',
            1 => 'l',
            2 => 'o',
        ],
    3 => [
            0 => 'l',
            1 => 'o',
            2 => ' ',
        ],
    4 => [
            0 => 'o',
            1 => ' ',
            2 => 'w',
        ],
    5 => [
            0 => ' ',
            1 => 'w',
            2 => 'o',
        ],
    6 => [
            0 => 'w',
            1 => 'o',
            2 => 'r',
        ],
    7 => [
            0 => 'o',
            1 => 'r',
            2 => 'l',
        ],
    8 => [
            0 => 'r',
            1 => 'l',
            2 => 'd',
        ],
    9 => [
            0 => 'l',
            1 => 'd',
            2 => 'h',
        ],
    10 => [
            0 => 'd',
            1 => 'h',
            2 => 'e',
        ],
];
*/

To reduce to the maximum the memory footprint, the library returns Generators, if you want to get the complete resulting array, use iterator_to_array().

API

Find the complete API documentation at https://not-a-number.io/phpngrams.

Code quality and tests

Every time changes are introduced into the library, Travis CI run the tests.

The library has tests written with PHPSpec.

Feel free to check them out in the spec directory. Run composer phpspec to trigger the tests.

PHPInfection is used to ensure that your code is properly tested, run composer infection to test your code.

Contributing

Feel free to contribute to this library by sending Github pull requests. I'm quite reactive :-)