Práctica elaborada por tí / Generador de contraseñas

<?php
  $charset = "abcdefghijklmnopqrstuvwxyx123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
$cad = "";
  for($i=0;$i<10;$i++) {
    $cad .= substr ($charset, rand (0, 61), 1);

}


?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Generador de Contraseñas</title>
</head>

<body>
<style type="text/css">
#caja{
    background:#B9DCFF;
    width:270px;
    height:220px;
    border:2px dotted black;
    margin:10px auto;
    padding:1em;
    border-radius:18px
}
h1,h2,h3,h4{
    font-family:arial;
    color:#ffffff;
}
input[type=text],input[type=password]{
    margin:0 0 1em 0;
    width:200px;
    border:0px;
    padding:1em;
    border-radius:3px;
}
input[type=submit], form a{
    padding:1em;
    background:#FC6;
    border:none;
    color:black;
    font-family:arial black;
    font-size:10px;
    border-radius:3px;
    text-decoration:none;

}
h1,h2,h3,h4{
    font-family:arial;
    color:#FFF;
}
h8{
    font-family
    color:#000;


}


<body>

}
</style>
<div id="caja">
  <div align="center">
    <form id="form1" name="form1" method="post" action="">
      <p><img src="https://cdn-icons.flaticon.com/png/512/5359/premium/5359937.png?token=exp=1647269042~hmac=3226305015904dceb0ba7c71c30cda5f" alt="" width="75" height="75" /></p>
      <p>
        <label for="user"></label>
      </p>
      <p>
        <input type="text" name="code" value="<?php echo $cad;?>" />
      </p>
      <p>
        <input type="submit" name="button" id="button" value="Guardar" />
      </p>
    </form>
    <p>&nbsp;</p>
  </div>
</div>
</body>
</html>