Untitled

<html>
<head>
<?php
    $lettera = $_POST["lettera"];
    if(isset($lettera)){
        include("connettoreDB.php");
        $lettera = strtoupper($lettera);
        $query = "SELECT CONCAT(s.Nome,' ',s.Cognome) as nominativo FROM `Studenti` as s, `Voti` as v WHERE s.Cognome LIKE '".$lettera."%' AND s.ID = v.ID_Studente AND v.Voto > 6 GROUP BY s.Cognome";
        $result = mysqli_query($link, $query);
        while($row = mysqli_fetch_array($result)){
            print($row["nominativo"]);
            print("<br>");
        }
    }
?>
</head>
<body>
<form name = "f1" method = "POST" action = "">
<select name = "lettera">
<option value="a">A</option>
<option value="b">B</option>
<option value="c">C</option>
<option value="d">D</option>
<option value="e">E</option>
<option value="f">F</option>
<option value="g">G</option>
<option value="h">H</option>
<option value="i">I</option>
<option value="l">L</option>
<option value="m">M</option>
<option value="n">N</option>
<option value="o">O</option>
<option value="p">P</option>
<option value="q">Q</option>
<option value="r">R</option>
<option value="s">S</option>
<option value="t">T</option>
<option value="u">U</option>
<option value="v">V</option>
</select>
<input type = "submit" value = "invio">
</form>
</body>
</html>