Wordpress checkbox into custom registration form - wordpress

Question

I've got my own custom registration form, and it allows people to register except for one small issue: the checkboxes don't do anything. When I check the meta_key fields in the database, they don't exist. Everything else is OK though.
I'm trying to have 'comps' and 'newsletter' get added to the meta_key fields (with a value of 1) when they checkboxes are ticked. My form looks like this:
<form id="form" action="<?php echo site_url('wp-login.php?action=register', 'login_post') ?>" method="post">
<fieldset>
<label for="user-login">Username<br />
<input type="text" name="user_login" id="user-login" class="input" value="" size="20" tabindex="10" />
<label for="user-email">Email address<br />
<input type="text" name="user_email" id="user-email" class="input" value="" size="25" tabindex="20" />
<label for="comps">Competitions<br />
<input type="checkbox" name="comps" id="comps" class="" value="1" tabindex="30" /></label>
<label for="newsletter">Newsletter<br />
<input type="checkbox" name="newsletter" id="newsletter" class="" value="1" tabindex="40" /></label>
<input type="hidden" name="redirect_to" value="<?php echo get_settings('home'); ?>/registration-succeeded"/>
<input type="submit" name="wp-submit" class="button" value="Register Me!" tabindex="100" />
</fieldset>
Is there something I need to do in functions.php of my theme to get these meta_fields to go into the database when the user registers (and when the checkboxes are ticked of course)?
Thanks in advance.

Answer 1

I've worked it out. Just needed to register these extra fields for metadata use:
function at_register_custom_fields( $user_id, $password = "", $meta = array() ) {
// custom fields
$fields = array(
'comps',
'newsletter',
);
// cleans and updates the custom fields
foreach ( $fields as $field ) {
$value = stripslashes( trim( $_POST[$field] ) ) ;
if ( ! empty( $value ) ) {
update_user_meta( $user_id, $field, $value );
}
}
}
add_action( 'user_register', 'at_register_custom_fields' );