creation of submenu in wordpress plugin creation - php

Question

I created a plugin and create a menu by using this code
add_filter('page_template', 'in_page_template');
function in_page_template()
{
global $wpdb;
$new_page_title = 'Packages';
$sql = "SELECT * FROM wp_posts where post_name='" . $new_page_title . "';";
$cnt_post = $wpdb->get_results($sql);
if (!(is_page('Home'))) {
$ppid = $_GET['page_id'];
if (count($cnt_post) != 0) {
$pid = $cnt_post[0]->ID;
if ($pid == $ppid) {
$page_template = dirname(__FILE__) . '/Packages.php';
return $page_template;
}
}
}
}
How can I create submenu for package page

Answer 1

add_action('init', 'create_initial_pages');
function create_initial_pages() {
$pages = array(
array(
'name' => 'post_name',
'title' => 'post_title',
'child' => array(
'page1-1' => 'National',
'page1-2' => 'International'
)
),
);
$template = array(
'post_type' => 'page',
'post_status' => 'publish',
'post_author' => 1
);
foreach( $pages as $page ) {
$exists = get_page_by_title( $page['title'] );
$my_page = array(
'post_name' => $page['name'],
'post_title' => $page['title']
);
$my_page = array_merge( $my_page, $template );
$id = ( $exists ? $exists->ID : wp_insert_post( $my_page ) );
if( isset( $page['child'] ) ) {
foreach( $page['child'] as $key => $value ) {
$child_id = get_page_by_title( $value );
$child_page = array(
'post_name' => $key,
'post_title' => $value,
'post_parent' => $id
);
$child_page = array_merge( $child_page, $template );
if( !isset( $child_id ) ) wp_insert_post( $child_page );
}
}
}
}