PHP脚本中的SQL查询

I have a database that consists of 3 tables.

1. user: 4 columns userId [primary key], name, emailId, password

2. residentController: 3 columns userId [foreign], departmentId [foreign], checkDefault checkDefault will be set to 1.

3. department with 6 columns: departmentId [primaryKey], departmentName, departmentDesc, departmentLink, checkDefault, departmentCategory

Here is the sequence that follows when a user registers for an android application. The following php script will be called.

It will add a record of the user into the database. After insertion of the data in the user table, I want to get all the "departmentNames" from department table and insert it into residentController. In the end, after particular user registers, then residentController must have these values populated into the residentController table.

userId  departmentId checkDefault
---------------------------------
1          1             1      
1          2             1      
1          3             1      
1          4             1      
1          5             1                  

Here is my php script.

<?php
require "init.php";
$fullname = "Fahman Khan";//$_POST["user"];
$emailid = "fxk120@hotmail.com";//$_POST["user_name"];
$userpass = "Windows";//$_POST["user_pass"];
$sql_query = "insert into user values(NULL,'$fullname','$emailid','$userpass')";
if(mysqli_query($connection, $sql_query))
{
echo "<h2> Data insertion success</h2>";
//Get the user id of the the registered user
$sql_queryTwo = "SELECT userId FROM user WHERE emailId='".$emailid."'";
//Store the result of the query in a variable
$result= mysqli_query($connection,$sql_queryTwo);
$row = mysqli_fetch_array($result);
//Retrive the user id
$data = $row[0];

//Insert default departments into residentController
}
else
{
//echo "Data insertion error".mysqli_error($connection);
}
?>

My question is that in my current php script, I don't know how I can insert departmentID into residentController table. departmentId is a foreign key and in my current department table there are 5 departments. I just need help writing the part in my php where I can insert in values into my residentController table. As of now, the current php script only adds a new user, but I need help inserting values into my residentController table.