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The Hoa\Ustring library. 2017-01-16 07:08 UTC



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Hoa is a modular, extensible and structured set of PHP libraries.
Moreover, Hoa aims at being a bridge between industrial and research worlds.


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This library allows to manipulate UTF-8 strings easily with some search algorithms.

Learn more.


With Composer, to include this library into your dependencies, you need to require hoa/ustring:

$ composer require hoa/ustring '~4.0'

For more installation procedures, please read the Source page.


Before running the test suites, the development dependencies must be installed:

$ composer install

Then, to run all the test suites:

$ vendor/bin/hoa test:run

For more information, please read the contributor guide.

Quick usage

We propose a quick overview of two usages: manipulate UTF-8 strings and one search algorithm.

Natural UTF-8 strings manipulation

The Hoa\Ustring\Ustring class allows to manipulate easily UTF-8 strings in a very natural way. This class implements the \ArrayAccess, \Countable and \IteratorAggregate interfaces. We will use the following examples:

$french   = new Hoa\Ustring\Ustring('Je t\'aime');
$arabic   = new Hoa\Ustring\Ustring('أحبك');
$japanese = new Hoa\Ustring\Ustring('私はあなたを愛して');

To get the first character, we will do:

    $french[0],  // string(1) "J"
    $arabic[0],  // string(2) "أ"
    $japanese[0] // string(3) "私"

And to get the last character, we will do [-1]. It supports unbounded (and modulo) indexes.

We note that it cares about text direction. Look at $arabic[0], it returns أ and not ك. To get the direction, we can use the Hoa\Ustring\Ustring::getDirection method (which call the Hoa\Ustring\Ustring::getCharDirection static method), it returns either Hoa\Ustring\Ustring::LTR (0) or Hoa\Ustring\Ustring::RTL (1):

    $french->getDirection(),  // int(0)
    $arabic->getDirection(),  // int(1)
    $japanese->getDirection() // int(0)

Text direction is also important for the append, prepend, pad… methods on Hoa\Ustring\Ustring for example.

To get the length of a string, we can use the count function:

    count($french),  // int(9)
    count($arabic),  // int(4)
    count($japanese) // int(9)

We are also able to iterate over the string:

foreach ($arabic as $letter) {

 * Will output:
 *     string(2) "أ"
 *     string(2) "ح"
 *     string(2) "ب"
 *     string(2) "ك"

Again, text direction is useful here. For $arabic, the iteration is done from right to left.

Some static methods are helpful, such as fromCode, toCode or isUtf8 on Hoa\Ustring\Ustring:

    Hoa\Ustring\Ustring::fromCode(0x1a9), // string(2) "Ʃ"
    Hoa\Ustring\Ustring::toCode('Ʃ'),     // int(425) == 0x1a9
    Hoa\Ustring\Ustring::isUtf8('Ʃ')      // bool(true)

We can also transform any text into ASCII:

$emoji = new Hoa\Ustring\Ustring('I ❤ Unicode');
$maths = new Hoa\Ustring\Ustring('∀ i ∈ ℕ');

    $emoji->toAscii(), "\n",
    $maths->toAscii(), "\n";

 * Will output:
 *     I (heavy black heart) Unicode
 *     (for all) i (element of) N

Search algorithm

The Hoa\Ustring\Search implements search algorithms on strings.

For example, the Hoa\Ustring\Search::approximated method make a search by approximated patterns (with k differences based upon the principle diagonal monotony). If we search the word GATAA in CAGATAAGAGAA with 1 difference, we will do:

$search = Hoa\Ustring\Search::approximated(
    $haystack = 'CAGATAAGAGAA',
    $needle   = 'GATAA',
    $k        = 1
$solutions = array();

foreach ($search as $pos) {
    $solutions[] = substr($haystack, $pos['i'], $pos['l']);

We will found AGATA, GATAA, ATAAG and GAGAA.

The result is not very handy but the algorithm is much optimized and found many applications.


The hack book of Hoa\Ustring contains detailed information about how to use this library and how it works.

To generate the documentation locally, execute the following commands:

$ composer require --dev hoa/devtools
$ vendor/bin/hoa devtools:documentation --open

More documentation can be found on the project's website: hoa-project.net.

Getting help

There are mainly two ways to get help:


Do you want to contribute? Thanks! A detailed contributor guide explains everything you need to know.


Hoa is under the New BSD License (BSD-3-Clause). Please, see LICENSE for details.