Function to base64 decode a string if it appears to be base64 encoded, or returns the string unchanged if it doesn't look like it's encoded.

base64_maybe.php

function base64_decode_maybe($str) {
    if (base64_encode(base64_decode($str, true)) == $str) {
        return base64_decode($str); 
    }
    return $str; 
}

I'd like to find a better way to check if it's encoded, but the only other solutions I've come across are regex matches looking for the right characters, and that lead to too many false positives. Decoding and encoding it back seems like an inefficient way to do this though. But, it works.