Detect base64 encoding in PHP?

Question

Is there some way to detect if a string has been base64_encoded() in PHP?

We\'re converting some storage from plain text to base64 and part of it lives in a cookie

Answer 1

Usually a text in base64 has no spaces.

I used this function which worked fine for me. It tests if the number of spaces in the string is less than 1 in 20.

e.g: at least 1 space for each 20 chars --- ( spaces / strlen ) < 0.05

function normalizaBase64($data){
    $spaces = substr_count ( $data ," ");
    if (($spaces/strlen($data))<0.05)
    {
        return base64_decode($data);
    }
    return $data;
}

Answer 2

May be it's not exactly what you've asked for. But hope it'll be usefull for somebody.

In my case the solution was to encode all data with json_encode and then base64_encode.

$encoded=base64_encode(json_encode($data));

this value could be stored or used whatever you need. Then to check if this value isn't just a text string but your data encoded you simply use

function isData($test_string){
   if(base64_decode($test_string,true)&&json_decode(base64_decode($test_string))){
      return true;
   }else{
    return false;
   }

or alternatively

function isNotData($test_string){
   if(base64_decode($test_string,true)&&json_decode(base64_decode($test_string))){
      return false;
   }else{
    return true;
   }

Thanks to all previous answers authors in this thread:)

Answer 3

Your best option is:

$base64_test = mb_substr(trim($some_base64_data), 0, 76);
return (base64_decode($base64_test, true) === FALSE ? FALSE : TRUE);

Answer 4

function is_base64_encoded($data)
{
    if (preg_match('%^[a-zA-Z0-9/+]*={0,2}$%', $data)) {
       return TRUE;
    } else {
       return FALSE;
    }
};

is_base64_encoded("iash21iawhdj98UH3"); // true
is_base64_encoded("#iu3498r"); // false
is_base64_encoded("asiudfh9w=8uihf"); // false
is_base64_encoded("a398UIhnj43f/1!+sadfh3w84hduihhjw=="); // false

http://php.net/manual/en/function.base64-decode.php#81425

Answer 5

base64_decode() will not return FALSE if the input is not valid base64 encoded data. Use imap_base64() instead, it returns FALSE if $text contains characters outside the Base64 alphabet imap_base64() Reference

Answer 6

I was about to build a base64 toggle in php, this is what I did:

function base64Toggle($str) {
    if (!preg_match('~[^0-9a-zA-Z+/=]~', $str)) {
        $check = str_split(base64_decode($str));
        $x = 0;
        foreach ($check as $char) if (ord($char) > 126) $x++;
        if ($x/count($check)*100 < 30) return base64_decode($str);
    }
    return base64_encode($str);
}

It works perfectly for me. Here are my complete thoughts on it: http://www.albertmartin.de/blog/code.php/19/base64-detection

And here you can try it: http://www.albertmartin.de/tools