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How to programmatically create child pages on theme activation.

$pages = array( 
    array(
        'name' => 'page1',
        'title' => 'Page 1',
        'child' => array(
            array(
                'name' => 'page11',
                'title' => 'Page 1.1'
            ),
            array(
                'name' => 'page12',
                'title' => 'Page 1.2'
            )
        )
    ),
    array(
        'name' => 'page2',
        'title' => 'Page 2',
        'child' => array(
            array(
                'name' => 'page21',
                'title' => 'Page 2.1'
            ),
            array(
                'name' => 'page22',
                'title' => 'Page 2.2'
            )
        )
    ),
    array(
        'name' => 'page3',
        'title' => 'Page 3',
        'child' => array(
            array(
                'name' => 'page21',
                'title' => 'Page 2.1'
            ),
            array(
                'name' => 'page22',
                'title' => 'Page 2.2'
            )
        )
    ),
);

$template = array(
    'post_type' => 'page',
    'post_status' => 'publish',
    'post_author' => 1
);

foreach( $pages as $page ) {
    $exists = get_page_by_title( $page['name'] );

    if( !$exists ) {
        $my_page = array(
            'post_name' => $page['name'],
            'post_title' => $page['title']
        );
        $my_page = array_merge( $my_page, $template );

        $id = wp_insert_post( $my_page );

        //if there is any child page, create them by {$id} as 'post_parent'
        if( isset( $page['child'] ) ) {
            foreach( $page['child'] as $child ) {
                $child_page = array(
                    'post_name' => $child['name'],
                    'post_title' => $child['title'],
                    'post_parent' => $id
                );
                $child_page = array_merge( $child_page, $template );
                $id = wp_insert_post( $child_page );
            }
        }
    }
}