php 用于检测 base64 编码字符串的 RegEx

RegEx for detecting base64 encoded strings

提问by federico-t

I need to detect strings with the form @base64(e.g. @VGhpcyBpcyBhbiBlbmNvZGVkIHN0cmluZw==) in my application.

我需要在我的应用程序中检测@base64（例如@VGhpcyBpcyBhbiBlbmNvZGVkIHN0cmluZw==）形式的字符串。

The @ has to be at the beginning and the charset for base64 encoded strings is a-z, A-Z, 0-9, +, /and =. Would be the appropiate regular expresion to detect them?

@ 必须在开头，base64 编码字符串的字符集是a-z, A-Z, 0-9, +,/和=。将是适当的正则表达式来检测它们吗？

Thanks

谢谢

回答by Regexident

Something like this should do (does not check for proper length!):

这样的事情应该做（不检查正确的长度！）：

^@[a-zA-Z0-9+/]+={,2}$

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The length of any base64 encoded string must be a multiple of 4, hence the additional.

任何 base64 编码字符串的长度必须是 4 的倍数，因此是额外的。

See here for a solution that checks against proper length: RegEx to parse or validate Base64 data

请参阅此处以获取检查正确长度的解决方案：RegEx to parse or validate Base64 data

A quick explanation of the regex from the linked answer:

链接答案中正则表达式的快速解释：

^@ #match "@" at beginning of string
(?:[A-Za-z0-9+/]{4})* #match any number of 4-letter blocks of the base64 char set
(?:
    [A-Za-z0-9+/]{2}== #match 2-letter block of the base64 char set followed by "==", together forming a 4-letter block
| # or
    [A-Za-z0-9+/]{3}= #match 3-letter block of the base64 char set followed by "=", together forming a 4-letter block
)?
$ #match end of string

回答by Federico Quagliotto

try with:

尝试：

^@(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$

=> RegEx to parse or validate Base64 data

=> RegEx 解析或验证 Base64 数据