W3cubDocs

/PHP

The Normalizer class

Introduction

(PHP 5 >= 5.3.0, PHP 7, PHP 8, PECL intl >= 1.0.0)

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

Changelog

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

Table of Contents

© 1997–2025 The PHP Documentation Group
Licensed under the Creative Commons Attribution License v3.0 or later.
https://www.php.net/manual/en/class.normalizer.php