create product gallery using POST method and wp-ajax

<?php
// Need to require these files
  if ( !function_exists('media_handle_upload') ) {
    require_once(ABSPATH . "wp-admin" . '/includes/image.php');
    require_once(ABSPATH . "wp-admin" . '/includes/file.php');
    require_once(ABSPATH . "wp-admin" . '/includes/media.php');
  }


// All data

$boat_title=$_POST['boattitle'];




$post = array(
    'post_author' => $user_id,
    'post_content' => '',
    'post_status' => "pending",
    'post_title' => $boat_title,
    'post_parent' => '',
    'post_type' => "product",
);
//Create post
$post_id = wp_insert_post( $post);

// set Featured Image , Let WordPress handle the upload.
 
  $attachment_id = media_handle_upload( 'my_boat_image_upload', $post_id );
  
  if ( is_wp_error( $attachment_id ) ) {
    // There was an error uploading the image.
    wp_send_json(array('status'=>false,'msg'=>"upload error"));
  } else {
    // The image was uploaded successfully!
    add_post_meta($post_id, '_thumbnail_id',$attachment_id);

  }



///.  Gallery Images....//


  $list_id="";
  
  $files = $_FILES["my_gallery"];  
    foreach ($files['name'] as $key => $value) {            
            if ($files['name'][$key]) { 
                $file = array( 
                    'name' => $files['name'][$key],
                    'type' => $files['type'][$key], 
                    'tmp_name' => $files['tmp_name'][$key], 
                    'error' => $files['error'][$key],
                    'size' => $files['size'][$key]
                ); 
                $_FILES = array ("my_gallery" => $file); 
        
                foreach ($_FILES as $file => $array) {              
                   
                    $attach_id= media_handle_upload( $file, $post_id);
                    $list_id=$attach_id.",".$list_id;
          
                }
            } 
        } 
    
 
update_post_meta($post_id,'_product_image_gallery',$list_id);


//if($post_id){
  //  $attach_id = get_post_meta($product->parent_id, "_thumbnail_id", true);
   // add_post_meta($post_id, '_thumbnail_id', $attach_id);
//}

wp_set_object_terms($post_id, 'Races', 'product_cat' );
wp_set_object_terms($post_id, 'simple', 'product_type');
update_post_meta( $post_id, '_visibility', 'visible' );
update_post_meta( $post_id, '_stock_status', 'instock');
update_post_meta( $post_id, 'total_sales', '0');
update_post_meta( $post_id, '_virtual', 'yes');
update_post_meta( $post_id, '_regular_price', "1" );
update_post_meta( $post_id, '_sale_price', "1" );
update_post_meta( $post_id, '_purchase_note', "" );


update_post_meta( $post_id, '_sale_price_dates_from', "" );
update_post_meta( $post_id, '_sale_price_dates_to', "" );
update_post_meta( $post_id, '_price', "1" );
update_post_meta( $post_id, '_sold_individually', "" );
update_post_meta( $post_id, '_manage_stock', "no" );

//wp_send_json($post_id);
?>