PHP 7.1.12 Released

分隔符

当使用 PCRE 函数的时候,模式需要由分隔符闭合包裹。分隔符可以使任意非字母数字、非反斜线、非空白字符。

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_-]%

如果分隔符需要在模式内进行匹配,它必须使用反斜线进行转义。如果分隔符经常在 模式内出现, 一个更好的选择就是是用其他分隔符来提高可读性。

/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。

除了上面提到的分隔符,也可以使用括号样式的分隔符,左括号和右括号分别作为开始和结束 分隔符。

{this is a pattern}

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

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User Contributed Notes 6 notes

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23
Pedro Gimeno
2 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
?>
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2
sln
1 year 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.
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3
Munin
2 years ago
preg_match('{[}]}', ''); // Warning: preg_match(): Unknown modifier ']'

preg_match('{[\}]}', ''); // OK
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1
Anonymous
28 days ago
check out the last user contributed note on this page

http://php.net/manual/en/regexp.reference.delimiters.php
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-2
hmelin at ya dot ru
1 year ago
A delimiter can be any ASCII non-alphanumeric, non-backslash, non-whitespace character:  !"#$%&'*+,./:;=?@^_`|~-  and  ({[<>]})
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-61
cissyyau77 at yahoo dot com dot hk
4 months ago
you guys can call me for sex
+852 92606871
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