How to add valdation by callback

Hello everybody.
I want to add some condition during the insert.
The condition uses more than one tables.
If support the condition then insert otherwise show mesage and not insert.
I attach a image.
Here amount field data entry depend on leave name field.

Example: if 'leave name' = 'Annual'

and 'amount' = 20.

I get the data annual leave balance from another table by using ;leave name' and check if 'amount' is greater than 'annual leave balance' then show wrong message.



public function leave_trans()

{

  $this->grocery_crud->set_table('nlg_leave_log');

  $this->grocery_crud->set_subject('Leave');

  $this->grocery_crud->required_fields('emp_id','amount','date_leave','leave_name');

  $this->grocery_crud->set_relation('emp_id','nlg_emp_info','emp_id');

  $this->grocery_crud->set_relation('leave_name','nlg_leave','leave_name');

  $this->grocery_crud->change_field_type('user','invisible');

  $this->grocery_crud->callback_before_insert(array($this,'leave_amount_check'));

  $this->grocery_crud->callback_before_insert(array($this,'user_calback'));

  $this->grocery_crud ->display_as('emp_id','Employee ID')

	   ->display_as('date_leave','Date Leave')

	   ->display_as('leave_name','Leave Name');



  $output = $this->grocery_crud->render();

  $this->crud_output($output);

}



function leave_amount_check($primary_key)

{

  $id = $primary_key;

  $amount = $post_array['amount'];

  $date_leave = $post_array['date_leave'];

  $leave_name = $post_array['leave_name'];

  $this->db->select('*');

  $this->db->where('id',$leave_name);



  $query = $this->db->get('nlg_leave');



  foreach ($query->result() as $row)

  {

   $leave_balance = $row->leave_balance;

  }

  if($amount > $leave_balance)

  {

   return false;

  }

  else

  {

   return true;

  }

}

This code is not working.
Please help.

.

How to add valdation by callback

tofayelahmed