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PHP的正则匹配小结

Jun 23, 2016 pm 01:18 PM

                      
 PCRE模式是PHP的正则匹配规则。
 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)这意味着例如preg_macth("[\w{2,3}]",$subject)这种类型的正则匹配也是可以的。当然常见的还是/\w{2,3}/这种,当里面需要转义的反斜线太多的时候,可以考虑用其他类型的分隔符进行闭合包裹。
 例如:/http:\/\// 可以写成@http ://@ 这种 也可以匹配到http://开头的。分隔符结束后,可以增加模式修饰符(模式修饰符其实是匹配功能的增强比如设置了i就会对大小写不敏感  m是进行多行匹配 s点号不匹配换行符号)
  基础正则使用小结:(最常用看到的匹配)
  \   反斜线转义的时候使用,匹配反斜线需要\\
  [abc] {2,5} 匹配abc中任何一个字母组成的2-5长度的字符串
  {^123$}m  匹配123开头结尾的行
三个字符串的等价使用:
*  = {0,}
+ ={1,}
? ={0,1}
   下面是preg_replace($pattern,$replace,$subject)的匹配进行例子讲解(实际中的正则匹配比语法复杂的多)         
1.正则匹配的分组调用

<?php$string = 'April 15, 2003';//对正则进行三重匹配 \w+的匹配\d+的匹配,\d+的匹配$pattern = '/(\w+) (\d+), (\d+)/i';//对匹配到的三个参数进行提取运用其中$1 $2  $3 分别代表对应三个变量$replacement = '${1}10,$3';//提取第一个和第三个匹配结果放到字符串里面 进行替换echo preg_replace($pattern, $replacement, $string);?>
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2.移除多余的空格正则匹配  \s代表匹配一个空格字符\s+代表匹配一个空格字符串+
$str = preg_replace('/\s\s+/', ' ', $str);
3.匹配的分组使用(可以把各种可能匹配到的正则填入正则数组,用后一个进行替换选择)
 preg_replace(array('/\d/', '/\s/'), '*', $str);
 4.?: 不匹配某个符号的用法 匹配到某个字符串结束
 preg_replace("/(?:)/i",$str, $result);
 匹配内的内容  同时用$str替换掉
 aaacdc  匹配到的是bbb


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