$str = 'test';
$cm = md5($str);
$bm = md5($str,true);

$cstr = implode(unpack('H*',$bm));
$bstr = pack('H*',$cm);

echo 'str:'. $str . "
\n";
echo 'cm :' . $cm . "
\n";
echo 'cstr:' . $cstr . "
\n";
echo 'urlencode(bm) :' . urlencode($bm) . "
\n";
echo 'urlencode(bstr):' . urlencode($bstr) . "
\n";