Detecting a Base_64encoded string

[Anon]

Hi,
Is it possible to determine if a string has been base64_encoded in PHP

Thanks

[Anon]

Purpose: To check whether a string is encoded with Base64

Base64 encoded string is in the following format:
=?ISO-2022-JP?B?vq7O07f1?=

Where =? Signals start of encoded string

ISO-2022-JP Charset name ("ISO-2022-JP" is for Japanese)

? Delimiter

B Encoding ("B" is for Base64)

? Delimiter

vq7O07f1 Example string of type "charset" encoded by "enco

?= Signals end of encoded string