LXXXVIII. Regular Expression Functions (Perl-Compatible)

Введение

The syntax for patterns used in these functions closely resembles Perl. The expression should be enclosed in the delimiters, a forward slash (/), for example. Any character can be used for delimiter as long as it's not alphanumeric or backslash (\). If the delimiter character has to be used in the expression itself, it needs to be escaped by backslash. Since PHP 4.0.4, you can also use Perl-style (), {}, [], and <> matching delimiters.

The ending delimiter may be followed by various modifiers that affect the matching. See Pattern Modifiers.

PHP also supports regular expressions using a POSIX-extended syntax using the POSIX-extended regex functions..

Требования

Regular expression support is provided by the PCRE library package, which is open source software, written by Philip Hazel, and copyright by the University of Cambridge, England. It is available at ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/.

Установка

Beginning with PHP 4.2.0 these functions are enabled by default. You can disable the pcre functions with --without-pcre-regex. Use --with-pcre-regex=DIR to specify DIR where PCRE's include and library files are located, if not using bundled library. For older versions you have to configure and compile PHP with --with-pcre-regex[=DIR] in order to use these functions.

Версия PHP для Windows-совместимых платформ имеет встроенную поддержку данного расширения. Это означает, что для использования данных функций не требуется загрузка никаких дополнительных расширений.

Настройка во время выполнения

Данное расширение не определяет никакие директивы конфигурации в php.ini.

Типы ресурсов

Данное расширение не определяет никакие типы ресурсов.

Предопределенные константы

Перечисленные ниже константы определены данным расширением и могут быть доступны только в том случае, если PHP был собран с поддержкой этого расширения или же в том случае, если данное расширение подгружается во время выполнения.

Таблица 1. PREG constants

constantdescription
PREG_PATTERN_ORDER Orders results so that $matches[0] is an array of full pattern matches, $matches[1] is an array of strings matched by the first parenthesized subpattern, and so on. This flag is only used with preg_match_all().
PREG_SET_ORDER Orders results so that $matches[0] is an array of first set of matches, $matches[1] is an array of second set of matches, and so on. This flag is only used with preg_match_all().
PREG_OFFSET_CAPTURE See the description of PREG_SPLIT_OFFSET_CAPTURE. This flag is available since PHP 4.3.0 .
PREG_SPLIT_NO_EMPTY This flag tells preg_split() to only return only non-empty pieces.
PREG_SPLIT_DELIM_CAPTURE This flag tells preg_split() to capture parenthesized expression in the delimiter pattern as well. This flag is available since PHP 4.0.5 .
PREG_SPLIT_OFFSET_CAPTURE If this flag is set, for every occuring match the appendant string offset will also be returned. Note that this changes the return value in an array where very element is an array consisting of the matched string at offset 0 and it's string offset into subject at offset 1. This flag is available since PHP 4.3.0 and is only used for preg_split().

Примеры

Пример 1. Examples of valid patterns

  • /<\/\w+>/

  • |(\d{3})-\d+|Sm

  • /^(?i)php[34]/

  • {^\s+(\s+)?$}

Пример 2. Examples of invalid patterns

  • /href='(.*)' - missing ending delimiter

  • /\w+\s*\w+/J - unknown modifier 'J'

  • 1-\d3-\d3-\d4| - missing starting delimiter

Содержание
Pattern Modifiers -- Describes possible modifiers in regex patterns
Pattern Syntax -- Describes PCRE regex syntax
preg_grep --  Return array entries that match the pattern
preg_match_all -- Perform a global regular expression match
preg_match -- Perform a regular expression match
preg_quote -- Quote regular expression characters
preg_replace_callback -- Perform a regular expression search and replace using a callback
preg_replace -- Perform a regular expression search and replace
preg_split -- Split string by a regular expression