ankitpokhrel / Dynamic-Featured-Image

        $thumbnail     = null;

        $attachment_id = null;

        if ( ! empty( $featured_img_full ) ) {

            $attachment_id = $this->get_image_id( $this->upload_url . $featured_img_full );

            $thumbnail = $this->get_image_thumb_by_attachment_id( $attachment_id, 'medium' );

            if ( empty( $thumbnail ) ) {

                // since medium sized thumbnail image is missing,

                // let's set full image url as thumbnail.

                $thumbnail = $featured_img_full;

            }

        }

        // Add a nonce field.

        echo $this->nonce_field( 'dfi_fimageplug-' . $featured_id ); // WPCS: XSS ok.

        $dfi_images = get_post_meta( $post_id, 'dfiFeatured', true );

        $ret_val    = array();

        if ( ! empty( $dfi_images ) && is_array( $dfi_images ) ) {

            foreach ( $dfi_images as $dfi_image ) {

                $dfi_image_full = $this->separate( $dfi_image, 'full' );

                $ret_val[]      = (int) $this->get_image_id( $this->upload_url . $dfi_image_full );

            }

        }

        return $ret_val;

    }