PHP - Insert Multiple Entries Into Multiple Tables

$error=array();
$sql = 'INSERT INTO staff(username, email, phone)
VALUES (?, ?, ?)';
$stmt = $conn->stmt_init();
$stmt = $conn->prepare($sql);
// bind parameters and insert the details into the database
$stmt->bind_param('sss', $username, $email, $phone);
$stmt->execute();
if ($stmt->errno == 1062) {
$errors[] = "One of the fields is already in use.";
}

<?php require_once("../includes/session.php");?>
<?php require_once("../includes/connection.php");?>
<?php require_once("../includes/function.php");?>
<?php confirm_logged_in();?>
<?php require_once("../includes/validation_functions.php");?>

<?php
if(isset($_POST['submit'])){

    //process the form
    // often there are form values in $_POST



        $product_name = mysql_prep($_POST["product_name"]);
        $product_amount = (int) $_POST["product_amount"];
        $visible = (int) $_POST["visible"];
    foreach($_FILES['files']['tmp_name'] as $key => $tmp_name ){
        $file_tmp =$_FILES['files']['tmp_name'][$key];
        $uploaded_dir = "images/"; 
        $filename = $_FILES['files']['name'][$key];
        $path = $uploaded_dir . $filename; 
        move_uploaded_file($file_tmp,"images/".$_FILES['files']['name'][$key]);

        $query  ="INSERT INTO products (";
        $query .=" name, amount, visible";
        $query .=") VALUES (";
        $query .=" '{$product_name}',{$product_amount},{$visible}";
        $query .=")";
        $result = mysqli_query($connection,$query);
        $last_id = mysqli_insert_id($connection);
        $sql.= "('$last_id','$path'),";
        $sql ="INSERT INTO images ( productID, file_name ) VALUES". trim($sql,',');
        $results = mysqli_query($connection,$sql);


        // validations
        $required_fields = array("product_name", "product_amount");
        validate_presences($required_fields);
        $fields_with_max_lenghts = array("product_name" => 30);
        validate_max_lenght($fields_with_max_lenghts);

        if(!empty($errors)){
            $_SESSION["errors"] = $errors;
            redirect_to("new_product.php");
        }
        if($result && $results ){
            // Sucess

            $_SESSION["message"] = "Product inserted.";
            redirect_to("manage_content.php");
        }else{
            // Failure

            $_SESSION["message"] = "Product insertion Failed.";
            redirect_to("new_product.php");
            }
        }
}else{
    // THis is probably a GET request
    redirect_to("new_product.php");
}
?>
<?php
if(isset($connnection)){
mysqli_close($connection);
}
?>

It would be GREAT if someone could provide some specific structural info for this:

I have one checkbox each for Moe, Larry, and Curly respectively.  I have managed to assemble code that allows for each of their names:

$sql="INSERT INTO $table (first_name) VALUES...

It works great INDIVIDUALLY.  But I want to be able to insert any combination into the $table by checking the respective checkboxes and submitting the form.

It seems that initiating more than a single INSERT will not get the job done, and separating the values as variables hasn't worked either.

What is required?  Can you offer an example?

<script>
$(document).ready(function(){
  $('#add').click(function(){
   var inp = $('#box');
   var i = $('input').size() + 1;
      $('<div id="box' + i +'"><input type="text" id="name" class="name" name="code[]' + i +'" placeholder="Input '+i+'"/><img src="remove.png" width="32" height="32" border="0" align="top" class="add" id="remove" /> </div>').appendTo(inp);
				
i++;
});
$('body').on('click','#remove',function(){
$(this).parent('div').remove();
});
});
</script>

<div id="box">
<input name = "code[]" type="text" id="name" class="name" placeholder="Input 1">
<img src="add.png" width="32" height="32" border="0" align="top" class="add" id="add" />
</div>

$rf = $_POST['regform'];
$b = $_POST['branch'];
$d = $_POST['date'];
$c = $_POST['code'];
$u = $_POST['user'];
				
for($i = 0; $i<count($c); $i++)
  {
    $a_query = mysql_query("INSERT INTO code_number(ts_number,branch_id,yy,code,username) VALUES('$rf','$b','$d','$c[$i]','$u')");
  }		
  return $a_query;

$i=0;
for($i){
$homerider=$home_rider[$i];
$homeorder=$order[$i];
$homesql="INSERT INTO tbl_lg_rider_order (`name`,`card_id`,`homeaway`,`riderorder`) VALUES ('$homerider',$card_id,'h','$homeorder')";
echo $homesql;
$i++;
}
$i=0;
for($i){
$awayrider=$away_rider[$i];
$awayorder=$awayorder[$i];
$homesql="INSERT INTO tbl_lg_rider_order (`name`,`card_id`,`homeaway`,`riderorder`) VALUES ('$awayrider',$card_id,'a','$awayorder')";
echo $awaysql;
$i++;
}