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Unicode character properties

Unicode character properties

Since 5.1.0, three additional escape sequences to match generic character types are available when UTF-8 mode is selected. They are:

\p{xx}_a character with the xx property\P{xx}a character without the xx property\X_an extended Unicode sequence

The property names represented by xx above are limited to the Unicode general category properties. Each character has exactly one such property, specified by a two-letter abbreviation. For compatibility with Perl, negation can be specified by including a circumflex between the opening brace and the property name. For example, \p{^Lu} is the same as \P{Lu}.

If only one letter is specified with \p or \P, it includes all the properties that start with that letter. In this case, in the absence of negation, the curly brackets in the escape sequence are optional; these two examples have the same effect:

\p{L} \pL

PropertyMatchesNotes
COther
CcControl
CfFormat
CnUnassigned
CoPrivate use
CsSurrogate
LLetterIncludes the following properties: Ll, Lm, Lo, Lt and Lu.
LlLower case letter
LmModifier letter
LoOther letter
LtTitle case letter
LuUpper case letter
MMark
McSpacing mark
MeEnclosing mark
MnNon-spacing mark
NNumber
NdDecimal number
NlLetter number
NoOther number
PPunctuation
PcConnector punctuation
PdDash punctuation
PeClose punctuation
PfFinal punctuation
PiInitial punctuation
PoOther punctuation
PsOpen punctuation
SSymbol
ScCurrency symbol
SkModifier symbol
SmMathematical symbol
SoOther symbol
ZSeparator
ZlLine separator
ZpParagraph separator
ZsSpace separator

Extended properties such as InMusicalSymbols are not supported by PCRE.

Specifying case-insensitive (caseless) matching does not affect these escape sequences. For example, \p{Lu} always matches only upper case letters.

Sets of Unicode characters are defined as belonging to certain scripts. A character from one of these sets can be matched using a script name. For example:

  • \p{Greek}

  • \P{Han}

Those that are not part of an identified script are lumped together as Common. The current list of scripts is:

ArabicArmenianAvestanBalineseBamum
BatakBengaliBopomofoBrahmiBraille
BugineseBuhidCanadian_AboriginalCarianChakma
ChamCherokeeCommonCopticCuneiform
CypriotCyrillicDeseretDevanagariEgyptian_Hieroglyphs
EthiopicGeorgianGlagoliticGothicGreek
GujaratiGurmukhiHanHangulHanunoo
HebrewHiraganaImperial_AramaicInheritedInscriptional_Pahlavi
Inscriptional_ParthianJavaneseKaithiKannadaKatakana
Kayah_LiKharoshthiKhmerLaoLatin
LepchaLimbuLinear_BLisuLycian
LydianMalayalamMandaicMeetei_MayekMeroitic_Cursive
Meroitic_HieroglyphsMiaoMongolianMyanmarNew_Tai_Lue
NkoOghamOld_ItalicOld_PersianOld_South_Arabian
Old_TurkicOl_ChikiOriyaOsmanyaPhags_Pa
PhoenicianRejangRunicSamaritanSaurashtra
SharadaShavianSinhalaSora_SompengSundanese
Syloti_NagriSyriacTagalogTagbanwaTai_Le
Tai_ThamTai_VietTakriTamilTelugu
ThaanaThaiTibetanTifinaghUgaritic
VaiYi

The \X escape matches a Unicode extended grapheme cluster. An extended grapheme cluster is one or more Unicode characters that combine to form a single glyph. In effect, this can be thought of as the Unicode equivalent of . as it will match one composed character, regardless of how many individual characters are actually used to render it.

In versions of PCRE older than 8.32 (which corresponds to PHP versions before 5.4.14 when using the bundled PCRE library), \X is equivalent to (?>\PM\pM*). That is, it matches a character without the "mark" property, followed by zero or more characters with the "mark" property, and treats the sequence as an atomic group (see below). Characters with the "mark" property are typically accents that affect the preceding character.

Matching characters by Unicode property is not fast, because PCRE has to search a structure that contains data for over fifteen thousand characters. That is why the traditional escape sequences such as \d and \w do not use Unicode properties in PCRE.

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