¿Cómo agrego elementos de contenido a un tipo de publicación personalizada mediante programación?

Primero debes ejecutar el wp_insert_post() que devolverá el ID de publicación. Luego use esa ID de publicación para agregar sus campos personalizados. Use add_post_meta() para agregar los campos personalizados.

$post_id = wp_insert_post( $args );

add_post_meta( $post_id, 'longitude', $my_long );
add_post_meta( $post_id, 'latitude', $my_lat );

Para adjuntos de imágenes, puede consultar esta pregunta: Cómo configurar la imagen destacada en una publicación personalizada desde el exterior mediante programación

Completamente sin probar, pero simplemente tiré esto juntos:

$post_data = array (
    'comment_status'    => 'closed',
    'ping_status'       => 'closed',
    'post_author'       => $author_id,
    'post_name'         => $slug,
    'post_title'        => $title,
    'post_status'       => 'publish',
    'post_type'         => 'custom-post-type', 
);

$post_ID = wp_insert_post( $post_data );

if ( ! is_wp_error( $post_ID ) ) {

    $post_meta = get_post_meta( $post_ID );

    if ( $post_meta ) {

        foreach ( $post_meta as $key => $value ) {

            if ( preg_match('/(\.jpg|\.png)$/', $value ) {

                $file = file_get_contents( $value );

                $tmpfname = tempnam( '/tmp',  'img' );

                $handle = fopen( $tmpfname );

                fwrite( $handle, $file );

                if ( getimagesize( $tmpfname ) ) {

                    $image_url  = $value;
                    $upload_dir = wp_upload_dir();
                    $image_data = file_get_contents( $image_url );

                    $filename   = end( explode( '/', $image_url ) );
                    $fileName   = end( explode( '/', $filename ) );

                    $uploadDir  = end( explode( 'uploads', $imageUrl ) );
                    $uploadDir  = str_replace( $fileName, '', $uploadDir );

                    $filename   = $fileName;

                    if ( wp_mkdir_p( $upload_dir['path'] ) ) {

                        $file = $upload_dir['basedir'] . $uploadDir . $filename;

                    } else {

                        $file = $upload_dir['basedir'] . $uploadDir . $filename;
                    }

                    file_put_contents( $file, $image_data );

                    $wp_filetype = wp_check_filetype( $filename, null );

                    $attachment = array (
                        'post_mime_type'    => $wp_filetype['type'], 
                        'post_title'        => sanitize_file_name( $filename ), 
                        'post_content'      => '', 
                        'post_status'       => 'inherit',
                    );

                    $attach_id = wp_insert_attachment( $attachment, $file, $post_ID );

                    // Include image.php
                    require_once(ABSPATH . 'wp-admin/includes/image.php');

                    $attach_data = wp_generate_attachment_metadata( $attach_id, $file );

                    wp_update_attachment_metadata( $attach_id, $attach_data );

                }

                fclose( $handle );

            } else {

                add_post_meta( $post_ID, $key, $value );

            }

        }

    }

}

El código debe ser autodocumentado, pero no dude en preguntar si tiene alguna pregunta o si no funciona.

Insertar y actualizar la publicación programáticamente. enlace

 if( $mydb->num_rows >  0) {

    echo 'Post '.$postCSVContent[0].' exist'.PHP_EOL;
    $template_file = get_post_meta( $postCSVContent[0], '_wp_page_template', true );
    echo 'Template File : '.$template_file.PHP_EOL;

    $updatePost = array(   
        'ID' => $postCSVContent[0],
        'post_title'    => $postCSVContent['1'],
        'post_content'  => $postCSVContent['2'],
        'post_type' => 'doors',
        'post_status'   => 'publish',
        'post_author'   => 1
    );

    wp_update_post( $updatePost );

    update_post_meta( $postCSVContent[0], '_wp_page_template', $template_file );
    updateAcf( $postCSVContent , $postCSVContent[0] );

}
else
{
    echo 'Post '.$postCSVContent[0].' is not existing'.PHP_EOL;        
    echo 'Post parent '.$parentId.PHP_EOL;

    $newIds = wp_insert_post( array(
            'post_title' => $postCSVContent['1'],
            'post_content' => $postCSVContent['2'],
            'post_type' => 'doors',
            'post_status' => 'publish',        
            'post_author'   => 1,
            'post_parent' => $parentId
    ));

    updateAcf( $postCSVContent , $newIds );

Consulte también el tutorial que actualiza acf. enlace

<?php
require_once 'wp-load.php'; //path of wp-load.php

$name = 'my post';
$content = 'dummy Content here';
$featured_image = 'fullimage url.jpg'; //pass here full image url

$post_data = array(
    'post_title'    => wp_strip_all_tags( $name ),
    'post_content'  => $content,
    'post_status'   => 'publish',
    'post_type'     => 'post',
    'post_author'   => 1,
    'post_category' => array(1,2),
    'page_template' => ''
);
$post_id = wp_insert_post( $post_data, $error_obj );

// for custom field
//add_post_meta( $post_id, 'post_date', 'Dec 5, 2018' ); // second parameter is your custom field name, 3rd parameter is value

generate_Featured_Image($featured_image, $post_id );

function generate_Featured_Image( $image_url, $post_id  ){
    $upload_dir = wp_upload_dir();
    $image_data = file_get_contents($image_url);
    $filename = basename($image_url);
    if(wp_mkdir_p($upload_dir['path']))
        $file = $upload_dir['path'] . '/' . $filename;
    else
        $file = $upload_dir['basedir'] . '/' . $filename;
    file_put_contents($file, $image_data);

    $wp_filetype = wp_check_filetype($filename, null );
    $attachment = array(
        'post_mime_type' => $wp_filetype['type'],
        'post_title' => sanitize_file_name($filename),
        'post_content' => '',
        'post_status' => 'inherit'
    );
    $attach_id = wp_insert_attachment( $attachment, $file, $post_id );
    require_once(ABSPATH . 'wp-admin/includes/image.php');
    $attach_data = wp_generate_attachment_metadata( $attach_id, $file );
    $res1= wp_update_attachment_metadata( $attach_id, $attach_data );
    $res2= set_post_thumbnail( $post_id, $attach_id );
    echo 'post created...';
}
?>