Is base 64 string encoded?

Question

How to determine if a string is data encoded with the base64_encode() function or not?

Is it possible?

Answer 1

Trying to decode it strictly against Base64 alphabet. The second parameter allows you to perform this rigorous check; Leaving this, the decoding function simply produces illegal characters before decoding:

 if (base64_decode($str, true) === false) { echo 'Not a Base64-encoded string'; } 

Answer 2

Try the following:

 if(base64_encode(base64_decode($img, true)) === $img) echo 'is a Base64-encoded string' ;