Perl-style regular expressions allow single-character options (flags) to be placed after the regular expression pattern to modify the interpretation or behavior of the match. For example, to do a case-insensitive match, you can simply use the i flag:
preg_match('/cat/i', 'Stop, Catherine!'); // returns true returns true
Table 4-12 shows the modifiers from Perl supported in Perl-compatible regular expressions:
Table 4-12: Perl flags
修饰符 |
意 义 |
/regexp/i |
不区分大小写的匹配 |
/regexp/s |
使句点(.)匹配任何字符,包括换行符(n) |
/regexp/x |
从模式中删除空白符和注释 |
/regexp/m |
使^匹配换行符 (n)之后的内容,美元符号($)匹配换行符 (n)之前的内容 |
/regexp/e |
如果替换字符串是PHP代码,使用eval()执行该代码来得到实际的替换字符串。 |
PHP's Perl-compatible regular expression functions also support other modifiers not supported in Perl, as shown in Table 4-13:
Table 4-13: Other PHP flags
修饰符 |
意 义 |
/regexp/U |
颠倒子模式的贪婪性;*和+尽可能少地匹配而不是尽可能多。 |
/regexp/u |
把模式字符串当作UTF-8编码对待 |
/regexp/X |
如果一个反斜杠之后跟着没有特殊意义的字符,将产生一个错误 |
/regexp/A |
把锚定位在字符串的开头就像模式中有^一样 |
/regexp/D |
使$字符仅匹配一行的末尾 |
/regexp/S |
使表达式解析器更加小心地检查模式的结构,使得第二次运行时(如在一个循环中)加快速度 |
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