Definite guide to valid Cookie values

Question

I know there are other questions but they seem to have answers which are assumptions rather than being definitive.

My limited understanding is that cookie values are

Answer 1

There was the mention of base64, so here is a cooked cookie solution using that in cookies. The functions are about a modified version of base64, they only use [0-9a-zA-Z_-]

You can use it for both the name and value part of cookies, is binary safe, as they say.

The gzdeflate/gzinflate takes back 30% or so space created by base64, could not resist using it. Note that php gzdeflate/gzinflate is only available in most hosting companies, not all.

//write
setcookie
         (
         'mycookie'
         ,code_base64_FROM_bytes_cookiesafe(gzdeflate($mystring))
         ,time()+365*24*3600
         );
//read
$mystring=gzinflate(code_bytes_FROM_base64_cookiesafe($_COOKIE['mycookie']));


function code_base64_FROM_bytes_cookiesafe($bytes)
    {
    //safe for name and value part [0-9a-zA-Z_-]
    return strtr(base64_encode($bytes),Array
            (
            '/'=>'_',
            '+'=>'-',
            '='=>'',
            ' '=>'',
            "\n"=>'',
            "\r"=>'',
            ));
    }


function code_bytes_FROM_base64_cookiesafe($enc)
    {
    $enc=str_pad($enc,strlen($enc)%4,'=',STR_PAD_RIGHT);//add back =
    $enc=chunk_split($enc);//inserts \r\n every 76 chars
    return base64_decode(strtr($enc,Array
            (
            '_'=>'/',
            '-'=>'+',
            )));
    }