function index() {
$submit = post('submit');

if ($submit == 'Submit') {
$this->validation_helper->set_rules('email', 'Email', 'required|valid_email|callback_otp_custom');

//run the validation tests
$result = $this->validation_helper->run();

if ($result == true) {
//echo 'well done';
$this->_generate_otp(post('email'));
} else {
validation_errors();
}
}

$this->view('login');
}

function otp_custom($email)
{
$error_msg = "Email not found in system. Please contact admin.";
return $error_msg;
die();
}

<h1><?= $headline ?></h1>
<?= validation_errors() ?>
<div class="card">
<div class="card-heading">
User Details
</div>
<div class="card-body">
<?php
echo form_open($form_location);
echo form_label('Name');
echo form_input('name', $name, array("placeholder" => "Enter Name"));
echo form_label('Email');
echo form_input('email', $email, array("placeholder" => "Enter Email"));
echo form_submit('submit', 'Submit');
echo anchor($cancel_url, 'Cancel', array('class' => 'button alt'));
echo form_close();
?>
</div>
</div>

function opt_custom($email) {
if ($email == '[email protected]') {
$error_msg = 'Sorry no eleetgeek emails allowed here!';
return $error_msg;
} else {
return true;
}
}

function index() {
$submit = post('submit');
if ($submit == 'Submit') {
$this->validation_helper->set_rules('email', 'Email', 'required|valid_email|callback_otp_custom');

//run the validation tests
$result = $this->validation_helper->run();

if ($result == true) {
echo 'well done';
} else {
//validation_errors();
}
}
$this->view('welcome');
}

function otp_custom($email)
{
if ($email == '[email protected]') {
$error_msg = 'Sorry no eleetgeek emails allowed here!';
return $error_msg;
} else {
return true;
}
}
}

&lt;!DOCTYPE html&gt;
&lt;html&gt;

&lt;body&gt;

&lt;h2&gt;Custom Validation Test Trongate!&lt;/h2&gt;

&lt;form method='POST'&gt;
&lt;?= validation_errors() ?&gt;
&lt;label for="email"&gt;Email&lt;/label&gt;&lt;br&gt;
&lt;input type="email" id="email" name="email" value=""&gt;&lt;br&gt;&lt;br&gt;
&lt;input type="submit" name="submit" value="Submit"&gt;&lt;br&gt;&lt;br&gt;
&lt;?= form_close() ?&gt;

&lt;/body&gt;

&lt;/html&gt;

function index() {
$submit = post('submit');

if ($submit == 'Submit') {
$this->validation_helper->set_rules('email', 'Email', 'required|valid_email|callback_otp_custom');

//run the validation tests
$result = $this->validation_helper->run();

if ($result == true) {
echo 'well done';
//$this->_generate_otp(post('email'));
}
}

$this->view('welcome');
}

function otp_custom($email) {
$error_msg = "Email not found in system. Please contact admin.";
return $error_msg;
}

function opt_custom($email) {
if ($email == '[email protected]') {
$error_msg = 'Email not found in system. Please contact admin.';
return $error_msg;
} else {
return true;
}
}

http://localhost/custom_validation_test/

http://localhost/custom_validation_test/test_validation

$target_module = ucfirst($this->url_segment(1));

// use default controller if there is no segment(1)
if ($target_module == NULL) {
$target_module = DEFAULT_CONTROLLER;

private function attempt_invoke_callback($key, $label, $posted_value, $test_to_run) {

$chars = substr($test_to_run, 0, 9);

if ($chars == 'callback_') {
$target_module = ucfirst($this->url_segment(1));
// use default controller if there is no segment(1)
if ($target_module == NULL) {
$target_module = DEFAULT_CONTROLLER;
}
$target_method = str_replace('callback_', '', $test_to_run);

if (!class_exists($target_module)) {
$modules_bits = explode('-', $target_module);
$target_module = ucfirst(end($modules_bits));
}

if (class_exists($target_module)) {

$static_check = new ReflectionMethod($target_module, $target_method);
if ($static_check->isStatic()) {
// STATIC METHOD
$outcome = $target_module::$target_method($posted_value);
} else {
// INSTANTIATED
$callback = new $target_module;
$outcome = $callback->$target_method($posted_value);
}

if (gettype($outcome) == 'string') {
$outcome = str_replace('{label}', $label, $outcome);
$this->form_submission_errors[] = $outcome;
}
}
}
}