add_noptin_subscriber( $fields )

function add_noptin_subscriber( $fields ) {
	global $wpdb;

	$table  = get_noptin_subscribers_table_name();
	$fields = wp_unslash( apply_filters( 'new_noptin_subscriber_fields', $fields ) );

	// Ensure an email address is provided and it doesn't exist already.
	if ( empty( $fields['email'] ) || ! is_email( $fields['email'] ) ) {
		return __( 'Please provide a valid email address', 'newsletter-optin-box' );
	}

	// Abort if the email is not unique.
	$fields['email'] = sanitize_email( $fields['email'] );
	$subscriber_id   = get_noptin_subscriber_id_by_email( $fields['email'] );
	if ( ! empty( $subscriber_id ) ) {
		return (int) $subscriber_id;
	}

	// Maybe split name into first and last.
	if ( isset( $fields['name'] ) ) {
		$names = noptin_split_subscriber_name( $fields['name'] );

		$fields['first_name'] = empty( $fields['first_name'] ) ? $names[0] : trim( $fields['first_name'] );
		$fields['last_name']  = empty( $fields['last_name'] ) ? $names[1] : trim( $fields['last_name'] );
	}

	$database_fields = array(
		'email'        => $fields['email'],
		'first_name'   => empty( $fields['first_name'] ) ? '' : $fields['first_name'],
		'second_name'  => empty( $fields['last_name'] ) ? '' : $fields['last_name'],
		'confirm_key'  => isset( $fields['confirm_key'] ) ? $fields['confirm_key'] :  md5( $fields['email']  . wp_generate_password( 32, true, true ) ),
		'date_created' => ! empty( $fields['date_created'] ) ? date( 'Y-m-d', strtotime( $fields['date_created'] ) ) : date( 'Y-m-d', current_time( 'timestamp' ) ),
		'active'       => isset( $fields['active'] ) ? (int) $fields['active'] :  ( get_noptin_option( 'double_optin' ) ? 1 : 0 ),
	);

	if ( ! $wpdb->insert( $table, $database_fields, '%s' ) ) {
		return 'An error occurred. Try again.';
	}

	$id = $wpdb->insert_id;

	$fields = array_merge( $fields, $database_fields );

	unset( $fields['last_name'] );
	unset( $fields['name'] );

	// Insert additional meta data.
	foreach ( $fields as $field => $value ) {

		if ( isset( $database_fields[ $field ] ) || 'name' === $field || 'integration_data' === $field ) {
			continue;
		}

		update_noptin_subscriber_meta( $id, $field, $value );
	}

	setcookie( 'noptin_email_subscribed', $database_fields['confirm_key'], time() + YEAR_IN_SECONDS, COOKIEPATH, COOKIE_DOMAIN );

	$cookie = get_noptin_option( 'subscribers_cookie' );
	if ( ! empty( $cookie ) && is_string( $cookie ) ) {
		setcookie( $cookie, '1', time() + YEAR_IN_SECONDS, COOKIEPATH, COOKIE_DOMAIN );
	}

	do_action( 'noptin_insert_subscriber', $id, $fields );

	return $id;

}