I'm looking for tool that generate random strings

<?
function code($limit)
	{
		return substr(md5(date("d.m.Y.H.i.s").rand(1,1000000000000000)) , 0 , $limit);
	}
$limit=rand(5,40);
echo code($limit);
?>

<?
  $charset="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
  $clen=strlen($charset)-1;
function code($len)
{
 global $charset;
 global $clen;
 for ($str="",$n=0;$n<$len;$n++,$str.=substr($charset,mt_rand(0,$clen),1));
 return $str;
}

for ($n=0;$n<10;$n++)
{
 $limit=mt_rand(10,20);
 echo code($limit);
 echo "\n";
}
?>