ปรึกษาเรื่องการ Random password แบบรูปภาพ กับ HTML

function random_password($len)
{
srand((double)microtime()*10000000);
$chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
$ret_str = "";
$num = strlen($chars);
for($i = 0; $i < $len; $i++)
{
$ret_str.= $chars[rand()%$num];
$ret_str.=""; 
}
return $ret_str; 
}
// echo random_password(8); 
$passw = random_password(7); 


$im = imagecreate(100, 100);

$string = '$passw ';

$bg = imagecolorallocate($im, 255, 255, 255);
$black = imagecolorallocate($im, 0, 0, 0);

// prints a black "P" in the top left corner
imagechar($im, 1, 0, 0, $string, $black);

header('Content-type: image/png');
imagepng($im);