Deret/Segitiga Huruf

<html>
<head>
<title>Segitiga Huruf</title>
</head>
<body>
<form action="for.php" method="post">
<input type="text" name="n"><br>
<input type="submit" value="proses"><br>
<?php
$n = isset($_POST['n']) ? $_POST['n'] : '';
if ($n>=27){
$n=26;
}else{$n=$n;}
for($k=1;$k<=$n;$k++){
    for($m=1;$m<=$k;$m++){
    echo chr(64+$m);
}
echo "<br>";
}
?>
</form>
</body>
</html>