bulk discount implementation

I have this controller whit this code which is currently(working) and need to implement bulk discount - 2-10 same items - 15%, 11-20 same items - 20%,30-50 same items - 25%

The problem is that right now in this big for loop i'm getting all the students and after that have another for loop to grab all the courses  but i'm doing that one by one and insert them in the db and doing all the transactions from the submitted form, 
In my situation I need to add those $mid's in one array to check them if i have two or more same $mid's and need to apply to proper discount if needed.

Code:

if ($errors_c==0) {

// ADD STUDENTS //
$uc=0;
$grade_ids = '';
$attach_receipt = 0;
for($i=1; $i<=$total_students; $i++) {
if ($this->input->post('fname_'.$i)!="" || $this->input->post('lname_'.$i)!="" || $this->input->post('email_'.$i)!="" || $this->input->post('userid_'.$i)!="" || $this->input->post('passwd_'.$i)!="") {
$userid_new="";
$iterate_mid="";
$course_names="";
$uc++;
$fname=$this->input->post('fname_'.$i);
$lname=$this->input->post('lname_'.$i);
$userid_new=$this->input->post('userid_'.$i);
$email=$this->input->post('email_'.$i);
$passwd=$this->input->post('passwd_'.$i);

if ($this->input->post('userid_'.$i)==$userid) {
$iterate_mid=$this->input->post('mid_'.$i.'_1');
$m_count++;
$data = array(
'fname' => $fname,
'lname' => $lname,
'module_id' => $iterate_mid
);
$this->db->where('id',$uid);
$this->db->update('t_users',$data);
$tmpid=$uid; }

if ($this->input->post('userid_'.$i)!=$userid) {
$passwd = $this->encrypt->encode($passwd);
$data = array(
'userid' => $userid_new,
'company' => $company,
'fname' => $fname,
'lname' => $lname,
'phone' => $phone,
'email' => $email,
'passwd' => $passwd,
'address' => $address,
'address2' => $address2,
'city' => $city,
'state' => $state,
'zip' => $zip,
'region' => $region,
'country' => 'US',
'cert_address' => $cert_address,
'cert_address2' => $cert_address2,
'cert_city' => $cert_city,
'cert_state' => $cert_state,
'cert_zip' => $cert_zip,
'cert_region' => $cert_region,
'cert_country' => '',
'company_id' => $company_id,
'module_id' => $mid,
'register_date' => $mysql_date_now,
'role_admin' => 'f',
'last_activity' => $mysql_date_now
);
$tmpid="";
$this->db->insert('t_users',$data);
$tmpid=$this->db->insert_id();

}

    $my_courses_ids[] = $s_courses;
$course_quantity = array_count_values($my_courses_ids);
foreach($my_courses_ids as $course_id) {
if(array_count_values($course_id) > 2) {

}
}
//Add selected courses
for($j=1; $j<5; $j++) {
$iterate_mid="";
$iterate_mid=$this->input->post('mid_'.$i.'_'.$j);
if ($iterate_mid!="1000" && $iterate_mid!="") {
$group_c++;
if ($this->input->post('userid_'.$i)==$userid) {
$this->session->set_userdata('current_module_id',$iterate_mid);
}
$mid=$iterate_mid;
$data = array(
'user_id' => $tmpid,
'module_id' => $mid
);
$this->db->insert('t_user_modules',$data);

$data = array(
'module_id' => $mid
);
$this->db->where('id',$tmpid);
$this->db->update('t_users',$data);

$price="0.00";
$this->db->from('t_modules');
$this->db->where("id", $mid);
$this->db->limit(1);
$query = $this->db->get();
$result = $query->result();
foreach ($result as $r) {
$price=$r->price;
$course_names.=$r->name.",";
}

$data = array(
'user_id' => $tmpid,
'module_id' => $mid,
'total' => $price,
'paid' => '',
'cardtype' => $cardtype,
'bill_email' => $bill_email,
'cardnum' => substr($cardnum, -4),
'po_num' => $po_num,
'po_fname' => $po_fname,
'po_lname' => $po_lname,
'po_email' => $po_email,
'status' => 'Open',
'auth_transactionid' => 0,
'auth_transactionststaus' => '',
'auth_captureamount' => 0,
'auth_refundamount' => 0,
'billto' => $UseCard ? $UseCard : 'C',
);

if($UseCard == 'I') {
$data['billto_status'] = 'Invoice Sent';
if ($CompanyData->is_billed_eom == 1) {
$data['billto_status'] = 'Invoice EOM';
$data['status'] = 'Closed';
}
}

$oid="";
$this->db->set('current_ts', 'NOW()', FALSE);
$this->db->set('order_date', 'NOW()', FALSE);
$this->db->insert('t_orders',$data);
$oid=$this->db->insert_id();

if ($this->input->post('userid_'.$i)==$userid) {
$this->session->set_userdata('ne_order_id',$oid);
}

$data = array(
'user_id' => $tmpid,
'quiz_id' => '20',
'module_id' => $mid,
'grade' => '',
'timer_h' => '0',
'timer_m' => '0',
'timer_s' => '0',
'exam_date' => $mysql_date_now, //'0000-00-00 00:00:00',
'cert_date' => $mysql_date_now, //'0000-00-00 00:00:00',
'certified' => 'f',
'answers' => '',
'order_id' => $oid
);
$current_grade_id="";
$this->db->insert('t_grades',$data);
$current_grade_id=$this->db->insert_id();
$grade_ids .= $current_grade_id.',';
if ($this->input->post('userid_'.$i)==$userid) {
// Set the session values for the Grade id
$this->session->set_userdata('current_grade_id',$current_grade_id);
$this->nativesession->set('current_grade_id',$current_grade_id);

}

$Amount = 0;


$Amount += $price;

if($UseCard != "I"){
if (!$Auth_PaymentProfileID)
{
$this->session->set_flashdata('message', "Could not get the Payment Details for these Orders");
$this->session->set_flashdata('messageClass','bad');
$errors_c = "33";
$errors = "Payment Failed 0";
}
if ($Amount == 0)
{
$this->session->set_flashdata('message', "Orders combined total is 0.00. Cannot process.");
$this->session->set_flashdata('messageClass','bad');
$errors_c = "33";
$errors = "Payment Failed 1";
}

if($errors_c == 0){

$Response = Transaction($Auth_CustomerID, $Auth_PaymentProfileID, $Amount, Array("duplicateWindow" => 0));
if ($Response["Status"] == "Success" )
{
if ($Response["Status"] == "Success")
{
$this->db->where('id', $oid);
$this->db->update('t_orders', Array("card_name" => '', "cardnum" => $CardNum, "expmonth" => '', "expyear" => '', "status"=>"Closed",
"billto_status" => "Payment Processed", "auth_transactionid" => $Auth_TransactionID, "auth_transactionststaus" => "Capture", "paid" => $Amount));

$this->orders_model->closeorder($oid); //changed for credit card success

$this->email_invoice_confirmation($EmailTo, $oid, $Amount);

$this->session->set_flashdata('message', "Orders have been charged and Updated.");
$this->session->set_flashdata('messageClass','good');
} else {
//failure - Update to "Payment Failed"
$this->db->where('id', $oid);
$this->db->update('t_orders', Array("billto_status" => "Payment Failed", "auth_transactionid" => $Auth_TransactionID, "auth_transactionststaus" => "Authorize"));
$errors_c = "33";
$errors = "Payment Failed 2";
$this->session->set_flashdata('message', "Order was authorized but could not be captured: ".$Response["Message"]);
$this->session->set_flashdata('messageClass','bad');
}
} else {
//failure - Update to "Payment Failed"

$this->db->where('id', $oid);
$this->db->update('t_orders', Array("billto_status" => "Payment Failed"));
$errors_c = "33";
$errors = "Payment Failed 3";
$this->session->set_flashdata('message', "Order could not be processed: ".$Response["Message"]);
$this->session->set_flashdata('messageClass','bad');
}
}
}
}
}
// END LOOP THROUGH THE COURSES
}

Was thinking on something like -  
$my_courses_ids[] = $mid;
//i will get the number of occurrences of the same ids(courses) from the form submitted
$course_quantity = array_count_values($my_courses_ids);
But really don't have an idea how to implement this.

Anyone have better idea?
Thank you.