create function to validate existing user / new user - php

Question

How do i check if the user already exist in the database. I can create user but not very sure how to check if the user already exist in the databas. here are my code:
view file
<?php echo $this->navigasi->top(); ?>
<div class="container">
<br>
<h4 style="margin:0 auto;width:650px;">CREATE USER ACCOUNT</h4>
<br>
<form class="form-horizontal the-form" method="post" action="<?php echo base_url(); ?>admin/register_account">
<?php echo $this->session->flashdata('mesej'); ?>
<div class="control-group">
<label class="control-label">Name Staff:</label>
<div class="controls">
<input type="text" required name="nama_staf" class="input-xlarge">
</div>
</div>
<div class="control-group">
<label class="control-label">Password:</label>
<div class="controls">
<input type="password" required name="kata_laluan" class="input-xlarge">
</div>
</div>
<div class="control-group">
<label class="control-label"> Email:</label>
<div class="controls">
<input type="email" name="email" class="input-xlarge">
</div>
</div>
<div class="control-group">
<label class="control-label">Position:</label>
<div class="controls">
<select name="jawatan" class="span3" id="jawatan">
<option value="1">Clerk</option>
<option value="2">Technician</option>
<option value="3">Assitant officer</option>
<option value="4">Officer</option>
<option value="5">Director</option>
</select>
</div>
</div>
<div class="control-group">
<label class="control-label">No. Staff:</label>
<div class="controls">
<input type="text" required name="no_staf" class="input-xlarge">
</div>
</div>
<div class="control-group">
<label class="control-label"></label>
<div class="controls">
<button type="submit" class="btn btn-primary"><i class="icon-user icon-white"></i> Register</button>
controller file
class Admin extends MY_Controller {
public function index()
{
$session_data = $this->session->userdata('account');
$data['sesi_jenis'] = $session_data['jenis'];
if($data['sesi_jenis'] < 1)
{
redirect('utama');
} else {
$this->load->view('view-utama-pentadbir');
}
}
public function register()
{
$this->load->view('view-create-account');
}
public function register_account()
{
$query = $this->modeluser->createAccount();
$this->session->set_flashdata('mesej', '<span class="label label-info">Account created!</span> ');
redirect(base_url().'admin/register');
model file
class ModelUser extends CI_Model {
public function creatAccount()
{
$nameStaf = $_POST['nama_staf'];
$noStaf = $_POST['no_staf'];
$email = $_POST['email'];
$password = sha1($_POST['password']);
$jenis = 0; // user is 0 - admin is 1
$position = $_POST['position'];
$this->db->query("INSERT INTO akaun (nama_staf,no_staf,email,password,jenis,position) VALUES ('$namaStaf','$noStaf','$email','$password','$jenis','$position')");
}
public function padamAkaun($no_staf)
{
$this->db->query("DELETE FROM akaun WHERE no_staf = '$no_staf'");
}

Answer 1

In your controller function set validation rule as:
$this->form_validation->set_rules('email', 'Email', trim|required|valid_email|is_unique[tabelname.columnname]|xss_clean');

Answer 2

change model as per.considering email is unique for each user
class ModelUser extends CI_Model {
public function creatAccount()
{
$nameStaf = $_POST['nama_staf'];
$noStaf = $_POST['no_staf'];
$email = $_POST['email'];
$password = sha1($_POST['password']);
$jenis = 0; // user is 0 - admin is 1
$position = $_POST['position'];
if ($this->checkEmailExist($email) == false)
return 'ERROR! DUPLICATE USER';// or handle as you like
$this->db->query("INSERT INTO akaun (nama_staf,no_staf,email,password,jenis,position)
VALUES ('$namaStaf','$noStaf','$email','$password','$jenis','$position')");
}
public function padamAkaun($no_staf)
{
$this->db->query("DELETE FROM akaun WHERE no_staf = '$no_staf'");
}
private function checkEmailExist($email)
{
$this->db->where('email', $email);
$query = $this->db->get('akaun');
if( $query->num_rows() == 0 ){ return TRUE; } else { return FALSE; }
}

Answer 3

$this->form_validation->set_rules('email', 'Email','trim|required|valid_email|is_unique[tabelname.columnname]|xss_clean');
$this->form_validation->set_error_delimiters('<div class="error">', '</div>');
if($this->form_validation->run() == TRUE)
{
// action after validation success.
}else{
//action after validation failure.
}