<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>Character classes</title>
</head>
<body><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="regexp.reference.dot.html">Dot</a></div>
<div class="next" style="text-align: right; float: right;"><a href="regexp.reference.alternation.html">Alternation</a></div>
<div class="up"><a href="reference.pcre.pattern.syntax.html">PCRE regex syntax</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div><hr /><div id="regexp.reference.character-classes" class="section">
<h2 class="title">Character classes</h2>
<p class="para">
An opening square bracket introduces a character class,
terminated by a closing square bracket. A closing square
bracket on its own is not special. If a closing square
bracket is required as a member of the class, it should be
the first data character in the class (after an initial
circumflex, if present) or escaped with a backslash.
</p>
<p class="para">
A character class matches a single character in the subject;
the character must be in the set of characters defined by
the class, unless the first character in the class is a
circumflex, in which case the subject character must not be in
the set defined by the class. If a circumflex is actually
required as a member of the class, ensure it is not the
first character, or escape it with a backslash.
</p>
<p class="para">
For example, the character class [aeiou] matches any lower
case vowel, while [^aeiou] matches any character that is not
a lower case vowel. Note that a circumflex is just a
convenient notation for specifying the characters which are in
the class by enumerating those that are not. It is not an
assertion: it still consumes a character from the subject
string, and fails if the current pointer is at the end of
the string.
</p>
<p class="para">
When case-insensitive (caseless) matching is set, any letters
in a class represent both their upper case and lower case
versions, so for example, an insensitive [aeiou] matches "A"
as well as "a", and an insensitive [^aeiou] does not match
"A", whereas a sensitive (caseful) version would.
</p>
<p class="para">
The newline character is never treated in any special way in
character classes, whatever the setting of the <a href="reference.pcre.pattern.modifiers.html" class="link">PCRE_DOTALL</a>
or <a href="reference.pcre.pattern.modifiers.html" class="link">PCRE_MULTILINE</a>
options is. A class such as [^a] will always match a newline.
</p>
<p class="para">
The minus (hyphen) character can be used to specify a range
of characters in a character class. For example, [d-m]
matches any letter between d and m, inclusive. If a minus
character is required in a class, it must be escaped with a
backslash or appear in a position where it cannot be
interpreted as indicating a range, typically as the first or last
character in the class.
</p>
<p class="para">
It is not possible to have the literal character "]" as the
end character of a range. A pattern such as [W-]46] is
interpreted as a class of two characters ("W" and "-")
followed by a literal string "46]", so it would match "W46]" or
"-46]". However, if the "]" is escaped with a backslash it
is interpreted as the end of range, so [W-\]46] is
interpreted as a single class containing a range followed by two
separate characters. The octal or hexadecimal representation
of "]" can also be used to end a range.
</p>
<p class="para">
Ranges operate in ASCII collating sequence. They can also be
used for characters specified numerically, for example
[\000-\037]. If a range that includes letters is used when
case-insensitive (caseless) matching is set, it matches the
letters in either case. For example, [W-c] is equivalent to
[][\^_`wxyzabc], matched case-insensitively, and if character
tables for the "fr" locale are in use, [\xc8-\xcb] matches
accented E characters in both cases.
</p>
<p class="para">
The character types \d, \D, \s, \S, \w, and \W may also
appear in a character class, and add the characters that
they match to the class. For example, [\dABCDEF] matches any
hexadecimal digit. A circumflex can conveniently be used
with the upper case character types to specify a more
restricted set of characters than the matching lower case type.
For example, the class [^\W_] matches any letter or digit,
but not underscore.
</p>
<p class="para">
All non-alphanumeric characters other than \, -, ^ (at the
start) and the terminating ] are non-special in character
classes, but it does no harm if they are escaped. The pattern
terminator is always special and must be escaped when used
within an expression.
</p>
<p class="para">
Perl supports the POSIX notation for character classes. This uses names
enclosed by <em>[:</em> and <em>:]</em> within the enclosing square brackets. PCRE also
supports this notation. For example, <em>[01[:alpha:]%]</em>
matches "0", "1", any alphabetic character, or "%". The supported class
names are:
<table class="doctable table">
<caption><strong>Character classes</strong></caption>
<tbody class="tbody">
<tr><td><em>alnum</em></td><td>letters and digits</td></tr>
<tr><td><em>alpha</em></td><td>letters</td></tr>
<tr><td><em>ascii</em></td><td>character codes 0 - 127</td></tr>
<tr><td><em>blank</em></td><td>space or tab only</td></tr>
<tr><td><em>cntrl</em></td><td>control characters</td></tr>
<tr><td><em>digit</em></td><td>decimal digits (same as \d)</td></tr>
<tr><td><em>graph</em></td><td>printing characters, excluding space</td></tr>
<tr><td><em>lower</em></td><td>lower case letters</td></tr>
<tr><td><em>print</em></td><td>printing characters, including space</td></tr>
<tr><td><em>punct</em></td><td>printing characters, excluding letters and digits</td></tr>
<tr><td><em>space</em></td><td>white space (not quite the same as \s)</td></tr>
<tr><td><em>upper</em></td><td>upper case letters</td></tr>
<tr><td><em>word</em></td><td>"word" characters (same as \w)</td></tr>
<tr><td><em>xdigit</em></td><td>hexadecimal digits</td></tr>
</tbody>
</table>
The <em>space</em> characters are HT (9), LF (10), VT (11), FF (12), CR (13),
and space (32). Notice that this list includes the VT character (code
11). This makes "space" different to <em>\s</em>, which does not include VT (for
Perl compatibility).
</p>
<p class="para">
The name <em>word</em> is a Perl extension, and <em>blank</em> is a GNU extension
from Perl 5.8. Another Perl extension is negation, which is indicated
by a <em>^</em> character after the colon. For example,
<em>[12[:^digit:]]</em> matches "1", "2", or any non-digit.
</p>
<p class="para">
In UTF-8 mode, characters with values greater than 128 do not match any
of the POSIX character classes.
</p>
</div><hr /><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="regexp.reference.dot.html">Dot</a></div>
<div class="next" style="text-align: right; float: right;"><a href="regexp.reference.alternation.html">Alternation</a></div>
<div class="up"><a href="reference.pcre.pattern.syntax.html">PCRE regex syntax</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div></body></html>
