# The Normalizer class

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## Introduction

Normalization is a process that involves transforming characters and sequences of characters into a formally-defined underlying representation. This process is most important when text needs to be compared for sorting and searching, but it is also used when storing text to ensure that the text is stored in a consistent representation.

The Unicode Consortium has defined a number of normalization forms reflecting the various needs of applications:

- Normalization Form D (NFD) - Canonical Decomposition
- Normalization Form C (NFC) - Canonical Decomposition followed by Canonical Composition
- Normalization Form KD (NFKD) - Compatibility Decomposition
- Normalization Form KC (NFKC) - Compatibility Decomposition followed by Canonical Composition

The different forms are defined in terms of a set of transformations on the text, transformations that are expressed by both an algorithm and a set of data files.

## Class synopsis

class Normalizer {
/* Constants */
public const int FORM_D;
public const int NFD;
public const int FORM_KD;
public const int NFKD;
public const int FORM_C;
public const int NFC;
public const int FORM_KC;
public const int NFKC;
public const int FORM_KC_CF;
public const int NFKC_CF;
/* Methods */
public static getRawDecomposition(string `$string`, int `$form` = `Normalizer::FORM_C`): ?string
public static isNormalized(string `$string`, int `$form` = `Normalizer::FORM_C`): bool
public static normalize(string `$string`, int `$form` = `Normalizer::FORM_C`): string|false
}

## Predefined Constants

The following constants define the normalization form used by the normalizer:

`Normalizer::FORM_C` int
  Normalization Form C (NFC) - Canonical Decomposition followed by Canonical Composition
`Normalizer::FORM_D` int
  Normalization Form D (NFD) - Canonical Decomposition
`Normalizer::NFD` int

`Normalizer::FORM_KC` int
  Normalization Form KC (NFKC) - Compatibility Decomposition, followed by Canonical Composition
`Normalizer::NFKC` int

`Normalizer::FORM_KC_CF` int

`Normalizer::FORM_KD` int
  Normalization Form KD (NFKD) - Compatibility Decomposition
`Normalizer::NFKD` int

`Normalizer::NFC` int

`Normalizer::NFKC_CF` int

## See Also

- » Unicode Normalization
- » Unicode Normalization FAQ
- » ICU User Guide - Normalization
- » ICU API Reference - Normalization

## Changelog

Version | Description
--- | ---
8.4.0 | The class constants are now typed.
8.0.0 | `Normalizer::NONE` has been removed.

## Table of Contents

- Normalizer::getRawDecomposition — Gets the Decomposition_Mapping property for the given UTF-8 encoded code point
- Normalizer::isNormalized — Checks if the provided string is already in the specified normalization form
- Normalizer::normalize — Normalizes the input provided and returns the normalized string

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