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PHP Manual

The Normalizer class

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

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

Normalizer {
/* Methods */
static bool isNormalized ( string $input [, string $form = Normalizer::FORM_C ] )
static string normalize ( string $input [, string $form = Normalizer::FORM_C ] )
}

Predefined Constants

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

Normalizer::FORM_C (string)
Normalization Form C (NFC) - Canonical Decomposition followed by Canonical Composition
Normalizer::FORM_D (string)
Normalization Form D (NFD) - Canonical Decomposition
Normalizer::FORM_KC (string)
Normalization Form KC (NFKC) - Compatibility Decomposition, followed by Canonical Composition
Normalizer::FORM_KD (string)
Normalization Form KD (NFKD) - Compatibility Decomposition
Normalizer::NONE (string)
No decomposition/composition
Normalizer::OPTION_DEFAULT (string)
Default normalization options

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