codeigniter displaying error message on same page - php

Question

another question again regarding codeigniter, here a few details:
view page:
<?php if (isset($error)){echo $error; } ?>
<form action="<?php echo site_url('mem_posting/post');>" method="post">
<input type="text" name="fname">
some fields goes here...
</form>
controller page(mem_posting):
public function post_form()
{
$this->load->view('header');
$this->load->view(form_page);
}
public function post()
{
$post_data=array(
'mem_id'=>$this->input->post('mem_id'),
//other inputs...
)
$this->load->model('member_model');
if ($this->member_model->check_member($post_data)===true)
{
//row exist
// **i would like to load the same page but
// **with error message "like already exist".
}else{
$this->member_model->inset_member($post_data);
}
}
model page:
public function insert_member($post_data=array())
{
extract($post_data);
$this->db->where('member_id', $member_id);
$this->db->insert('membership', $post_data);
}
public function check_member($post_data=array())
{
extract($post_data);
$this->db->select('mem_id');
$this->db->where('mem_id', $mem_id);
$query = $this->db->get('membership');
if ($query->num_rows() > 0){
return true;
}else{
return false;
}
}
as you can see the view page contains the form, now what i would like to achieve is to echo an error like 'already exist' so i dont have to code another $this->load->view('post_form') inside the if statement.
thank you in advance..

Answer 1

Do you mean just sending a variable to the view?
$data['error'] = "error message";
$this->load->view('some/view', $data);

Answer 2

Well! you shoul run validation when your form is submited. So, imagine you have 2 fields submited. It would be like this:
$this->form_validation->set_rules('name', 'Name', 'required|trim|xss_clean');
$this->form_validation->set_rules('mem_id', 'ID Member', 'required|trim|is_unique[yourtable.mem_id]|xss_clean');
if ($this->form_validation->run()){
// Do your cool stuff now because validation passed
}else{
// Whatever...validation fails, load your view.
}
So in your view you shoul have somethin like this at top of the form:
<?php echo validation_errors(); ?>
is_unique[yourtable.mem_id] will validate if the input is unique in your DB. So if is really unique, OK.