MYSQL insert into multiple tables doesn't work - php

Question

I have three files reg_form.php, dbconnection.php and insert.php.
When submitting the form the data is not inserted into the database. I can't figure out why. Initially I didn't know how to use insert into multiple tables but took the advice of many posts from here. Unfortunately I have still failed to make it work and it is driving me insane. Here is the sql code so far for the insert.
<?php
include ("dbconnection.php");
if(file_exists("dbconnection.php")) {
echo"Connected to database successfully";
} else if(!file_exists("dbconnection.php")){
echo "Connection failed";
}
$forename = "forename";
$surname = "surname";
$address_line1 = "address_line1";
$address_line2 = "address_line2";
$address_line3 = "address_line3";
$city = "city";
$postcode = "postcode";
$phone = "phone";
$email = "email";
$username = "username";
$password = "password";
$cpassword = "cpassword ";
$query = "INSERT INTO users (username,
password)VALUES('$username','$password');";
$query2 = "INSERT INTO users_details (forename, surname,address_line1,
address_line2, address_line3, city, postcode, phone, email)
VALUES('$forename','$surname','$address_line1','$address_line2',
'$address_line3','$city','$postcode','$phone','$email')";
query ($dbconnection,$sql);
?>

Answer 1

Ok problem is solved. I made a stored procedure because I am doing an INSERT INTO multiple tables and then called it like this.
$sql ="CALL add_user('".$username."', '".$password."', 'user',
'".$forename."','".$surname."', '".$address_line1."' ,
'".$address_line2."', '".$address_line3."', '".$city."', '".$postcode."',
'".$phone."', '".$email."','".is_bool($email_contact)."',
'".is_bool($phone_contact)."')";
$query = $con->prepare($sql);
$query->execute();