correcting the connection when querying the database

var/www/messageSender.php

@@ -24,13 +24,13 @@ $username = $_POST["name"];
 $message = $_POST["message"];
 
 $query0 = "Select max(messageID) from messages";
-mysqli_query($db, $query0) or die('Error querying database.');
-$maxID = mysqli_query($db, $query0);
+mysqli_query($conn, $query0) or die('Error querying database.');
+$maxID = mysqli_query($conn, $query0);
 $maxID = $maxID + 1;
 $query1 = "Insert into messages (messageID, sender, recipient, message, date, haveread) values({$maxID}, , {$username}, {$message}, NOW(), 'N')";
-mysqli_query($db, $query1) or die('Error inserting into database.');
+mysqli_query($conn, $query1) or die('Error inserting into database.');
 
-mysqli_close($db);
+mysqli_close($conn);
 ?>
 
 </body>