2012-02-17 18:17
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I've already got a bit of working code but I need someone to help explain why it works if they can!

I am using PHP to replace anything in a string if it is not either a-z, A-Z, 0-9, a comma, a semicolon, an underscore or a hyphen (which ultimately should represent either a single username, or a comma/semicolon separated list of usernames).

The following works:

$data = preg_replace('/[^,;a-zA-Z0-9_-]/s', '', $data);

But the following does not:

$data = preg_replace('/[^a-zA-Z0-9_-,;]/s', '', $data);

Why will this only work when the comma and semicolon are at the start? Putting them at the end seems to break things (this is what I tried initially when I came across /[^a-zA-Z0-9_-]/s.

As an aside, I am also using the following to trim any trailing semicolons (plural) or commas (plural) and someone may be able to suggest a more efficient and/or elegant way to do this?:

if(preg_match('/;$/', $data))
    $data = rtrim($data, ';' );
if(preg_match('/,$/', $data))
    $data = rtrim($data, ',' );

Thanks for any help :)

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我使用PHP替换字符串中的任何内容,如果它不是az,AZ,0-9,逗号,分号,下划线或连字符(最终应该代表) 单个用户名,或逗号/分号分隔的用户名列表。)


  $ data = preg_replace(  '/ [^,; a-zA-Z0-9 _-] / s','',$ data); 

但以下内容不是:< / p>

  $ data = preg_replace('/ [^ a-zA-Z0-9 _-,;] / s','',$ data); 

为什么只有在逗号和分号开头时才能使用它? 把它们放在最后似乎打破了事情(这是我最初尝试时遇到的事情/ [^^a-zA-Z0-9_-]/s.


除此之外, 我还使用以下内容修剪任何尾随分号(复数)或逗号(复数),有人可能会建议一种更有效和/或更优雅的方法来执行此操作?:

  if(preg_match('/; $ /',$ data))
 $ data = rtrim($ data,';'); 
(preg_match  ('/,$ /',$ data))
 $ data = rtrim($ data,','); 


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3条回答 默认 最新

  • duandian2725 2012-02-17 18:31

    It's not the comma and semicolon causing your problem; it's the hyphen. Look at the parts of your character class and consider what they mean:

    0-9 # Anything from '0' to '9', meaning 0, 1, 2, ... 9
    A-Z # Anything from 'A' to 'Z', meaning A, B, C, ... Z
    _-, # Anything from '_' to ',', meaning...uh...hmmm.

    There's no clear progression from _ to ,, so the regex engine isn't sure what to make of this. In character classes, if you want a hyphen to be interpreted literally, it needs to be at the very beginning or end of the class (or escaped with a backslash). So any of these will work:


    As for trimming off the end, you can do all of this in one regex replace:

    $data = preg_replace('/[^,;a-zA-Z0-9_-]|[,;]$/s', '', $data);
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  • duansen6750 2012-02-17 18:20

    I believe it's the placement of the hyphen that matters -- has to be at start or end to be a hyphen (literal), otherwise it's being used to define a range.

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  • dongtan7998 2012-02-17 18:26

    You can escape the hyphen and put it anywhere in the regex like this \-

    As for the trailing semicolons and commas, try this /[,;]+$/ it should match any commas and semicolons at the end even if they are many.

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