ต้องการเพิ่มข้อมูล ลงตารางที่ 2 มี foreign key จากตารางที่ 1 ต้องเขียนอย่างไรค่ะ

<?php
require 'connectdb.php';

if(isset($_POST['submit'])){ 
    if (empty($_POST['firstname'])){
    echo 'Could you please fill in this form?';
    header("Location:index.php");
    exit();
} else {
    $firstname = mysqli_real_escape_string($dbcon,$_POST['firstname']);
}
$aca_id = $_POST['aca_id'];
$lastname = $_POST['lastname'];
$department = $_POST['department'];
$faculty = $_POST['faculty'];
$university =$_POST['university'];
$email =$_POST['email'];
$mobile =$_POST['mobile'];
$expertise =$_POST['expertise'];
$review_preference =$_POST['review_preference'];


//upload CV
$ext = pathinfo(basename($_FILES['cv']['name']),PATHINFO_EXTENSION);
$new_ab_name = 'cv_'.uniqid().".".$ext;
$file_path = "cv/";
$upload_path = $file_path.$new_ab_name;


$success = move_uploaded_file($_FILES['cv']['tmp_name'], $upload_path);
if ($success==FALSE){
    echo 'ไม่สามารถ upload CV'. mysqli_error($dbcon);
    exit();
}
$cv = $new_ab_name;
$q = "INSERT INTO reviewers (aca_id,firstname,lastname,department,faculty,university,email,mobile,cv,expertise,review_preference) VALUES ('$aca_id','$firstname','$lastname','$department','$faculty','$university','$email','$mobile','$cv','$expertise','$review_preference')";
$result = mysqli_query($dbcon, $q) or die($dbcon->error.'<br>'. $q);
    
    $gradArr = $_POST['grad'];    
    $grad_fieldArr = $_POST['grad_field'];
    $grad_yearArr = $_POST['grad_year'];
    $grad_instArr = $_POST['grad_inst'];
    if(!empty($gradArr)){
        $rev_id = mysqli_insert_id($dbcon);
        for($i = 0; $i < count($gradArr); $i++){
            if(!empty($gradArr[$i])){ 
                $grad = $gradArr[$i];                
                $grad_field = $grad_fieldArr[$i];
                $grad_year = $grad_yearArr[$i];
                $grad_inst = $grad_instArr[$i];
                
                //database insert query goes here                                
                $q = "INSERT INTO education (rev_id,grad,grad_field,grad_year,grad_inst) VALUES ('$rev_id','$grad','$grad_field','$grad_year','$grad_inst')";
$result = mysqli_query($dbcon, $q);

            }
        }
    } 
}
if($result){
    echo 'เพิ่มข้อมูลเรียบร้อยแล้ว';
    header("Location:index.php");    
}else {
    echo 'เกิดข้อผิดพลาดในการเพิ่มข้อมูล'. mysqli_error($dbcon);   
}
mysqli_close($dbcon);