Unable to update product gallery image on woocommerce programatically - wordpress

Question

I'm trying to edit product from frontend. I have a issue on updating gallery images when I have submit only profile image only uploaded and gallery image was not updated to product gallery images. here is my sample code for gallery images.
<input type="file" name="product_gallery[]" id="edit_product_gallery" multiple accept=".jpg,.jpeg,.png,.gif,.bmp,.tiff">
$('#update_product').submit( function(e){
e.preventDefault();
$('#submit').prop('disabled', true);
let apiUrl = '<?=get_home_url(); ?>/wp-admin/admin-ajax.php';
let product_gallery = document.getElementById('edit_product_gallery').files;
// Read selected files
var form = new FormData();
var totalfiles = document.getElementById('edit_product_gallery').files.length;
for (var index = 0; index < totalfiles; index++) {
form.append("product_gallery[]", document.getElementById('edit_product_gallery').files[index] );
}
form.append('product_id', <?=$product_id; ?>);
form.append('user_id', '<?=$user_id; ?>');
form.append('action', 'edit_productss');
jQuery.ajax({
url: apiUrl,
type: "post",
data: form,
processData: false,
contentType: false,
beforeSend: function (data) {
$("#overlay-loader").show(300);
},
success: function (response) {
if(response.data.status == 'success') {
console.log(response.data.status);
}else{
console.log(response.data.message);
}
},
complete: function (data) {
$("#overlay-loader").fadeOut();
}
});
});
add_action('wp_ajax_nopriv_edit_productss', 'edit_productss');
add_action('wp_ajax_edit_productss', 'edit_productss');
function edit_product() {
$user_id = sanitize_text_field( $_POST['user_id'] );
$product_id = sanitize_text_field( $_POST['product_id'] );
$files = $_FILES;
if ( !empty( $files ) ) {
// key as product image, product_gallery value files
foreach ( $files as $key => $file ) {
if( empty( $file ) ) continue;
$attachment_id = $attchment_ids[] = media_handle_upload( $key, $upload_overrides );
if ( is_wp_error( $attachment_id )) {
$error[] = $attachment_id;
}
}
}
$attchment_ids = !empty( $attchment_ids ) ? implode(',', $attchment_ids ) : '';
// UPDATE PRODUCT GALLERY IMAGE IDS TO DB
$result = update_post_meta( $product_id ,'_product_image_gallery', $attchment_ids );
$response['status'] = $result ? "Success" : 'Failure';
$response['error'] = $error;
wp_send_json_success($response);
}
Hi, I'm trying to edit product from frontend. I have a issue on updating gallery images when I have submit only profile image only uploaded and gallery image was not updated to product gallery images. here is my sample code for gallery images.