php 正则表达式只允许字母数字、逗号、连字符、下划线和分号
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Regex to only allow alphanumeric, comma, hyphen, underscore and semicolon
提问by Robin
I've already got a bit of working code but I need someone to help explain why it works if they can!
我已经有了一些工作代码，但我需要有人帮助解释为什么它可以工作！
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).
我正在使用 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（最终应表示单个用户名或逗号/分号分隔）用户名列表）。
The following works:
以下工作：
$data = preg_replace('/[^,;a-zA-Z0-9_-]/s', '', $data);
But the following does not:
但以下没有：
$data = preg_replace('/[^a-zA-Z0-9_-,;]/s', '', $data);
Why will this only work when the comma and semicolon are at the start? Putting them at the end seems to break things (this is what I tried initially when I came across /[^a-zA-Z0-9_-]/s.
为什么这仅在逗号和分号位于开头时才有效？将它们放在最后似乎会破坏事情（这是我最初遇到 /[^a-zA-Z0-9_-]/s 时尝试的。
As an aside, I am also using the following to trim any trailingsemicolons (plural) or commas (plural) and someone may be able to suggest a more efficient and/or elegant way to do this?:
顺便说一句，我还使用以下内容来修剪任何尾随分号（复数）或逗号（复数），有人可能会建议一种更有效和/或更优雅的方法来做到这一点？：
if(preg_match('/;$/', $data))
{
$data = rtrim($data, ';' );
}
if(preg_match('/,$/', $data))
{
$data = rtrim($data, ',' );
}
Thanks for any help :)
谢谢你的帮助 ：）
回答by Justin Morgan
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:
不是逗号和分号导致您的问题；这是连字符。查看角色类的各个部分并考虑它们的含义：
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:
从_到没有明确的进展,，因此正则表达式引擎不确定如何处理。在字符类中，如果您希望从字面上解释连字符，则它需要位于类的开头或结尾（或用反斜杠转义）。所以这些都可以工作：
[^,;a-zA-Z0-9_-]
[^-,;a-zA-Z0-9_]
[^a-zA-Z0-9_\-,;]
As for trimming off the end, you can do all of this in one regex replace:
至于修剪结束，您可以在一个正则表达式替换中完成所有这些：
$data = preg_replace('/[^,;a-zA-Z0-9_-]|[,;]$/s', '', $data);
回答by Devin Ceartas
I believe it's the placement of the hyphen that matters -- has to be at start or end to be a hyphen (literal), otherwise it's being used to define a range.
我相信重要的是连字符的位置 - 必须在开头或结尾才能成为连字符（文字），否则它被用来定义一个范围。
回答by iDifferent
You can escape the hyphen and put it anywhere in the regex like this \-
您可以像这样转义连字符并将其放在正则表达式中的任何位置 \-
As for the trailing semicolons and commas, try this /[,;]+$/it should match any commas and semicolons at the end even if they are many.
至于尾随的分号和逗号，试试这个，/[,;]+$/它应该匹配末尾的任何逗号和分号，即使它们很多。
