PHP - Manual: 分隔符

2024-12-21

分隔符

当使用 PCRE 函数的时候，模式需要由分隔符闭合包裹。分隔符可以是任意非字母数字、非反斜线、非空白字符。静默忽略合法分隔符之前的空白字符。

经常使用的分隔符是正斜线(/)、hash符号(#) 以及取反符号(~)。下面的例子都是使用合法分隔符的模式。

/foo bar/
#^[^0-9]$#
+php+
%[a-zA-Z0-9_-]%

It is also possible to use bracket style delimiters where the opening and closing brackets are the starting and ending delimiter, respectively. (), {}, [] and <> are all valid bracket style delimiter pairs.

(this [is] a (pattern))
{this [is] a (pattern)}
[this [is] a (pattern)]
<this [is] a (pattern)>

Bracket style delimiters do not need to be escaped when they are used as meta characters within the pattern, but as with other delimiters they must be escaped when they are used as literal characters.

如果需要在正则模式内匹配分隔符，必须使用反斜线转义。如果分隔符经常在正则模式内出现，最好使用其他分隔符以便提高可读性。

/http:\/\//
#http://#

需要将一个字符串放入模式中使用时，可以用 preg_quote() 函数对其进行转义，它的第二个参数(可选)可以用于指定需要被转义的分隔符。

可以在结束分隔符后面增加模式修饰符。下面的例子是一个大小写不敏感的匹配：

#[a-z]#i

add a note

User Contributed Notes 6 notes

down

Pedro Gimeno ¶

7 years ago


Note that bracket style opening and closing delimiters aren't a 100% problem-free solution, as they need to be escaped when they aren't in matching pairs within the expression. That mismatch can happen when they appear inside character classes [...], as most meta-characters lose their special meaning. Consider these examples:

<?php
  preg_match('{[{]}', ''); // Warning: preg_match(): No ending matching delimiter '}'
  preg_match('{[}]}', ''); // Warning: preg_match(): Unknown modifier ']'
  preg_match('{[}{]}', ''); // Warning: preg_match(): Unknown modifier ']'
?>

Escaping them solves it:

<?php
  preg_match('{[\{]}', ''); // OK
  preg_match('{[}]}', ''); // OK
  preg_match('{[\}\{]}', ''); // OK
?>

down

Revo ¶

3 years ago


Note that angle brackets `<>` shouldn't be used as delimiters whenever you will have to invoke advanced clusters like atomic groups or lookbehinds because their including angle bracket doesn't come in pair and escaping doesn't help either.

down

Munin ¶

6 years ago


preg_match('{[}]}', ''); // Warning: preg_match(): Unknown modifier ']'

preg_match('{[\}]}', ''); // OK

down

-3

rawr dot t dot regx at gmail dot com ¶

2 years ago


You might also use T-Regx library, which has automatic delimiters:

pattern('Foo(Bar)?')->test($text);

down

-19

sln ¶

6 years ago


The dirty little delimiter secret they don't tell you ->
Examples: Balanced delims {\d{2}Some\\{33\\}\w{5}} parses to
\d{2}Some\\{33\\}\w{5} and {\d{2}Some\{33\}\w{5}} parses to \d{2}Some{33}\w{5}.  
Un-Balanced delims +\d{2}Some\+33\+\w{5}+ parses to \d{2}Some+33+\w{5} and
+\d{2}Some\\+33\\+\w{5}+ won't parse because the delimiter is unescaped.

down

-28

hmelin at ya dot ru ¶

6 years ago


A delimiter can be any ASCII non-alphanumeric, non-backslash, non-whitespace character:  !"#$%&'*+,./:;=?@^_`|~-  and  ({[<>]})

add a note

官方地址：https://www.php.net/manual/en/regexp.reference.delimiters.php

有任何技术问题请点击这里网站运营推广招聘

IT PHP 编程语言 Linux 开发编程科技 Elasticsearch HTML/CSS/XML 网络数据库 JAVA 面试 NoSQL C/C++ Golang Git 算法操作系统正则表达式 Redis 互联网 MySql JavaScript 运维软件国际架构设计 Mac OS TCP/IP Excel Vim Windows Socket Oracle VR MongoDB Python 运营 MemCache 商业硬件电子娱乐设计 nginx 摄影游戏 WordPress HTTP 团建数码电器

php7 安装fileinfo扩展 preg_split — 通过一个正则表达式分隔字符串 php位值,解决 PHP 中 usort 在值相同时改变原始位置的问题 [PHP] inet_pton/inet_ntop IP地址转换函数 PHP 8.1 [鸟哥]PHP_INT_MIN 和 -9223372036854775808 ADORecordSet对象 adodb手册 opcache预加载 Composer的Packagist资源 array_multisort() 多字段排序 PHPMailer设置utf8 PHPMailer字符集CharSet PHP json解析（json_decode）页面工具 mysql面试题 [原创]诡异的php-fpm超时问题 php中几种注释规范纯php实现DES以及TripleDES加密算法 php 修改图片大小 PHP5 扩展SOAP 调用 webservice [鸟哥]PHP FFI详解 - 一种全新的PHP扩展方式

略微加速

PHP官方手册 - 互联网笔记

分隔符

User Contributed Notes 6 notes