Drupal custom registration Form element not showing on frontend - php

Question

My problem is that, I want to add a select dropdown in registration form to choose user type. But this code not shows the form element on front end. Can somebody please look at the code and tell me what's wrong with that code. I can see the array which is contains this element but not showing in the registration form.
Please check here is my code below:
<?php
function registration_role_dropdown_form_alter($form, &$form_state, $form_id){
if ($form_id == 'user_register_form') {
/*$query = db_select('role', 'r');
$query->addTag('translatable');
$query->fields('r', array('rid', 'name'));
$query->orderBy('weight');
$query->orderBy('name');
if (!empty($permission)) {
$query->innerJoin('role_permission', 'p', 'r.rid = p.rid');
$query->condition('p.permission', $permission);
}
$result = $query->execute();*/
$form['account']['roles']= array(
'#type' => 'select',
'#title' => t('Register As'),
'#options' => array(
registration_role_dropdown_user_roles()
),
'#description' => t('Select the <em>User type</em> from the dropdown.'),
);
}
}
function registration_role_dropdown_user_roles($membersonly = FALSE, $permission = NULL) {
$query = db_select('role', 'r');
$query->addTag('translatable');
$query->fields('r', array('rid', 'name'));
$query->orderBy('weight');
$query->orderBy('name');
if (!empty($permission)) {
$query->innerJoin('role_permission', 'p', 'r.rid = p.rid');
$query->condition('p.permission', $permission);
}
$result = $query->execute();
$roles = array();
foreach ($result as $role) {
switch ($role->rid) {
// We only translate the built in role names
case DRUPAL_ANONYMOUS_RID:
if (!$membersonly) {
$roles[$role->rid] = t($role->name);
}
break;
case DRUPAL_AUTHENTICATED_RID:
$roles[$role->rid] = t($role->name);
break;
default:
$roles[$role->rid] = $role->name;
}
}
return $roles;
}
?>

Answer 1

You aren't passing the $form variable by reference so your changes to it are never passed back to the callee of your hook_form_alter implementation.
Change:
function registration_role_dropdown_form_alter($form, &$form_state, $form_id)
to
function registration_role_dropdown_form_alter(&$form, &$form_state, $form_id)
Note the addition of the ampersand before the $form parameter.
Side note: Drupal's convention is to not close the opening <?php tag in your module files.