function from10to64($base10) {
    $ret = "";
    if ( $base10 > 0 ) {
        while ( $base10 > 0 ) {
            $rem = $base10 % 64;
            $base10 = floor($base10 / 64);
            $ret = char64($rem) . $ret;
        }
    } else {
        $ret = "0";
    }
    return $ret;
}

function from64to10($base64) {
    $ret = 0;
    if ( strlen($base64) > 0 ) {
        $exp = 1;
        for ( $i = strlen($base64) - 1; $i >= 0; $i-- ) {
            $dig = substr($base64, $i, 1);
            $ret += (char10($dig) * $exp);
            $exp = $exp * 64;
        }
    } else {
        $ret = 0;
    }
    return $ret;
}

function char64($num) {
    if ( $num >= 0 && $num <= 9 ) return "" . $num;
    else if ( $num >= 10 && $num <= 35 ) return chr($num + 55);
    else if ( $num >= 36 && $num <= 61 ) return chr($num + 61);
    else if ( $num == 62 ) return "-";
    else if ( $num == 63 ) return "_";
}

function char10($dig) {
    $asc = ord($dig);
    
    if ( $asc == 95 ) return 63;
    else if ( $asc == 45 ) return 62;
    else if ( $asc >= 97 && $asc <= 122 ) return $asc - 61;
    else if ( $asc >= 65 && $asc <= 90 ) return $asc - 55;
    else if ( $asc >= 48 && $asc <= 57 ) return $asc - 48;
}