验证用户名是否为带下划线的字母数字 [英] Validate username as alphanumeric with underscores

问题描述

在我的注册页面上，我需要仅将用户名验证为字母数字，还需要带有可选的下划线.我想出了这个:

On my registration page I need to validate the usernames as alphanumeric only, but also with optional underscores. I've come up with this:

function validate_alphanumeric_underscore($str) 
{
    return preg_match('/^\w+$/',$str);
}

哪个看起来还可以，但是我不是正则表达式专家！有人发现任何问题吗?

Which seems to work okay, but I'm not a regex expert! Does anyone spot any problem?

推荐答案

实际的

The actual matched characters of \w depend on the locale that is being used:

单词"字符是任何字母或数字或下划线字符，即可以成为Perl" 单词 "的一部分的任何字符.字母和数字的定义由PCRE的字符表控制，如果进行特定于语言环境的匹配，则可能会有所不同.例如，在"fr"(法语)语言环境中，某些大于128的字符代码用于带重音的字母，并且这些字符由\ w匹配.

A "word" character is any letter or digit or the underscore character, that is, any character which can be part of a Perl "word". The definition of letters and digits is controlled by PCRE's character tables, and may vary if locale-specific matching is taking place. For example, in the "fr" (French) locale, some character codes greater than 128 are used for accented letters, and these are matched by \w.

因此，您最好明确指定要允许的字符:

So you should better explicitly specify what characters you want to allow:

/^[A-Za-z0-9_]+$/

这仅允许使用字母数字字符和下划线.

This allows just alphanumeric characters and the underscore.

如果您只想将下划线用作连接字符，并且要强制用户名必须以字母字符开头:

And if you want to allow underscore only as concatenation character and want to force that the username must start with a alphabet character:

/^[A-Za-z][A-Za-z0-9]*(?:_[A-Za-z0-9]+)*$/

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