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

We can combine three things into one function to check if given string is a valid base 64 encoded or not.

function validBase64($string)
{
    $decoded = base64_decode($string, true);

    // Check if there is no invalid character in string
    if (!preg_match('/^[a-zA-Z0-9\/\r\n+]*={0,2}$/', $string)) return false;

    // Decode the string in strict mode and send the response
    if (!$decoded) return false;

    // Encode and compare it to original one
    if (base64_encode($decoded) != $string) return false;

    return true;
}