My code is not inserting data into database - php

Question

I had an old mysql code where it successfully inserted values into the database. But as that people are now stating that mysqli is better to use (can't use PDO because of my version of php is below 5.3), I have tried to change my code so that it uses mysqli instead of mysql.
The problem is that it now does not insert values into the database since making this change. I am a mysqli novice so I would really appreciate it if somebody can help me change the code below so that mysqli can be used to insert data into the database. What am I doing wrong? There are no errors in the error report.
Below is my current attempt on this:
$username="xxx";
$password="xxx";
$database="mobile_app";
$mysqli = new mysqli("localhost", $username, $password, $database);
/* check connection */
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
die();
}
$sql = "SELECT TeacherId FROM Teacher WHERE (TeacherUsername = ?)";
$stmt=$mysqli->prepare($sql);
$stmt->bind_param("s",$_SESSION['teacherusername']);
$stmt->execute();
$record = $stmt->fetch();
$teacherid = $record['TeacherId'];
if($_SERVER['REQUEST_METHOD'] == 'POST')
{
$time = str_replace(array(' Hrs ', ' Mins ', ' Secs'), array(':', ':', ''), $_SESSION['durationChosen']);
$insertsql = "INSERT INTO Session (SessionId, SessionTime, SessionDate, SessionWeight, SessionDuration, TotalMarks, ModuleId, TeacherId, Room) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)";
$insert = $mysqli->prepare($insertsql);
for ($i = 1, $n = $_SESSION['sessionNum']; $i <= $n; ++$i) {
$sessid = $_SESSION['id'] . ($n == 1 ? '' : $i);
$sessdate = date("Y-m-d", strtotime($_SESSION['dateChosen']));
$insert->bind_param("sssssssss", $sessid, $_SESSION['timeChosen'], $sessdate,
$_SESSION['textWeight'], $time, $_SESSION['textMarks'],
$_SESSION['module'], $teacherid, $_SESSION['rooms']);
$insert->execute();
}
}

Answer 1

Looks like you're missing the ending quote on this line:
$insertsql = "INSERT INTO Session (
SessionId, SessionTime, SessionDate, SessionWeight,
SessionDuration, TotalMarks, ModuleId, TeacherId, Room)
VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?);
Make it
$insertsql = "INSERT INTO Session (
SessionId, SessionTime, SessionDate, SessionWeight,
SessionDuration, TotalMarks, ModuleId, TeacherId, Room)
VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)";
It also looks like you need to put your for loop before you bind the params, since you're using the results of said for loop in the bind.