Problem creating a query in MySQL via PHP [closed]

I´m trying to connect with MySQL and create a query, but I’m unable and I don’t know why. Hope you can help.

This is my code

$host="myhost";
$username="myusername";
$password= "mypw";
$db="mydB";
$conn = mysqli_connect($host,$username,$password,$database);
if (!$conn) {
    die("Conection failed: " . mysqli_connect_error());
}
else
{
echo "Connected successfully";
}
$sql="SELECT * FROM Books ORDER BY Downloads DESC LIMIT 50";
$result = mysqli_query($conn, $sql);
if (!$result) {
    die("Query error: " . mysqli_error($conn));
}
if (mysqli_num_rows($result) > 0)
 {
    echo "<table id='menu'><tr><td>ID</td><td>Name Book</td><td>Downloads</td></tr>";
  while ($row = mysqli_fetch_assoc($result))
   {
     $U = $row['Link'];
     $Title = $row['Title'];
     $plat= $row['Genre'];
    echo "<tr><td><font color='black'><p align='left'><ul type='square'><li><a href='$U' target='blank' title='Download $Titulo $plat Book'>".$Title."</a>(".$plat.")</li></ul></font>";
     }
     echo "</td></tr></table>";
}
else
{
die ("cannot connect");
}
mysqli_close($conn);
?>

Thank you in advance