PDO multiple inserts only insert last value from multiple checkboxes - php

Question

I am trying to insert data into my db using PDO. I have been successful until now but the following error has happened to me and I do not know the reason.
My goal is to insert data into three different tables at once ussing transactions. In the last two tables the records come from multiple checkboxes and store them as an array is not an option. I have been successful in storing the multiple values from the checkboxes when I only use first two queries but as soon as I add the third query in the transaction only the last value from the while is included into the database.
It's very strange because when I save the data into the user and language table using the while it works fine including all data but when I added the third query. The program stops working as I intended and the data base only receive the last record for both language and education table.
I get the following data from a html form and I send it to the class:
if($_POST){
// set values to object properties
$user->firstname=$_POST['firstname'];
$user->lastname=$_POST['lastname'];
$user->user_id=$_SESSION['user_id'];
// Data for the language table, second query in class function
while(list($key,$value) = each($_POST['language']))
{$user->language=$value;}
while(list($key,$value) = each($_POST['level']))
{$user->level=$value;}
// Data for the education table, third query in class function
while(list($key,$value) = each($_POST['studies']))
{$user->studies=$value;}
while(list($key,$value) = each($_POST['insti']))
{$lawyer->institution=$value;}
while(list($key,$value) = each($_POST['from']))
{$user->from_start=$value;}
while(list($key,$value) = each($_POST['to']))
{$user->to_end=$value;}
// create the user
if($user->registeruser()){
echo "<div class=\"alert alert-info\">";
echo "Registration completed, thank you. In the following 24 hours a member of our team will contact you. ";
echo "</div>";
}else{
echo "<div class=\"alert alert-danger\" role=\"alert\">Unable to register. Please try again.</div>";
}
}
The class function is written as follow:
function registeruser(){
try {
$this->conn->beginTransaction();
$query = "UPDATE
users
SET
firstname = :firstname,
lastname = :lastname,
WHERE
id = :id";
// prepare query statement
$stmt = $this->conn->prepare($query);
// bind variable values
$stmt->bindParam(':firstname', $this->firstname);
$stmt->bindParam(':lastname', $this->lastname);
$stmt->bindParam(':id', $this->user_id);
// execute the query
$stmt->execute();
$query = 'INSERT INTO language (user_id,language,level) VALUES (?,?,?)';
$stmt = $this->conn->prepare($query);
$stmt->bindParam(1, $this->user_id);
$stmt->bindParam(2, $this->language);
$stmt->bindParam(3, $this->level);
$stmt->execute();
$query = 'INSERT INTO education (user_id,studies,school,from_start,to_end) VALUES (?,?,?,?,?)';
$stmt = $this->conn->prepare($query);
$stmt->bindParam(1, $this->user_id);
$stmt->bindParam(2, $this->studies);
$stmt->bindParam(3, $this->institution);
$stmt->bindParam(4, $this->from_start);
$stmt->bindParam(5, $this->to_end);
$stmt->execute();
$this->conn->commit();
return true;
} catch (Exception $e) {
$stmt->rollBack();
return false;
}
}
Thank you in advance.
PD: There is not error from db or php code. The problem is that the second and third query in the transaction are not inserting the multiple values from checkboxes into the DB, only the last. When I only include two queries into the transaction all values from the checkboxes are included the different table.