Download multiples files as zip in WordPress

/**
 * Download multiples files at once in WordPress
 */
function vdm_files_downloads() {

    if ( 
        ! isset( $_POST['vdm_download_nonce'] ) 
        || ! wp_verify_nonce( $_POST['vdm_download_nonce'], 'vdm_download_action' ) 
        || !isset($_POST['vdm_download_files'])
        || empty($_POST['vdm_download_files'])
        || !is_user_logged_in()
    ) {
       return;
    }

    /**
     * Get current user data
     */
    $current_user = wp_get_current_user();
    
    /**
     * Start Download Process
     */

    $download_files = (array) $_POST['vdm_download_files'];
    $download_files = array_map( 'intval', $download_files );

    /**
     * Folder name
     */
    $foldername = "vdm-downloaded-files-by-{$current_user->user_login}/";

    $new_data = array();
    
    /**
     * Get current user ID
     */
    $user_id = $current_user->ID;

    // get current date
    $current = date('m/d/Y h:i:s a', time());
    $timestamp = strtotime($current);

    // get old data
    $old_data = get_user_meta($user_id, '_vdm_download_info', true);

    /**
     * Get site current upload dir and path
     */
    $upload_dir = wp_get_upload_dir();
    $filepath = $upload_dir['path'] . '/';

    /**
     * Naming the file. you can change it as you wish.
     */
    $filename = 'vdm-download-files-' .uniqid() . "-" . $user_id . ".zip";

    /**
     * Full location for the zip. where it should be saved.
     * 
     */
    $mainFile = $filepath.$filename;

    /**
     * Make sure ZipArchive is available
     */
    if( !class_exists( 'ZipArchive' ) ) {
        esc_html_e('Sorry, this side did not support PHP default library "ZipArchive".', 'textdomain');
        exit;
    }

    $kire = [];

    /**
     * Start create zip file using default php library : ZipArchive
     * 
     * @link https://www.php.net/manual/en/class.ziparchive.php
     * @link https://www.php.net/manual/en/ziparchive.addfile.php
     * 
     */
    $zip = new ZipArchive;
    $zip->open($mainFile, ZipArchive::CREATE);
    
    foreach ($download_files as $file) {
        
        /**
         * Get attachment file url
         */
        $url = get_attached_file((int)$file);
        if ( !isset( $url ) || !file_exists( $url ) ) {
            return;
        }

        $kire[] = $url;
        
        /**
         * Then input in zip file
         */
        $zip->addFile($url, $foldername . basename($url));

        if ( !empty( $old_data ) && array_key_exists($file, $old_data) ) {
            $old_data[$file]['date'][] = $current;
        } else {
            $new_data[$file]['date'][] = $current;
            $new_data[$file]['size'] = $timestamp;
        }

    }
    
    if ($zip->close() === false) {
        exit("Error creating ZIP file");
    };

    /**
     * Before download make sure your zip has been created successfully.
     */
    if (file_exists($mainFile)) {

        if ( !empty( $old_data ) && !empty($new_data) ) {
            $new_data = $old_data + $new_data;
        } elseif ( !empty( $old_data ) && empty( $new_data ) ) {
            $new_data = $old_data;
        }
        
        update_user_meta($user_id, '_vdm_download_info', $new_data);

        /**
         * Clean before start download
         */
        ob_end_clean();

        /**
         * Get zip file size
         */
        $filesize = filesize($mainFile);

        /**
         * http headers for zip downloads
         * 
         * @link https://perishablepress.com/http-headers-file-downloads/
         */
        header("Pragma: public");
        header("Expires: 0");
        header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
        header("Cache-Control: public");
        header("Content-Description: File Transfer");
        header("Content-type: application/octet-stream");
        header("Content-Disposition:attachment; filename=\"".$filename."\"");
        header("Content-Transfer-Encoding: binary");
        header("Content-Length: ".$filesize);
        ob_end_flush();
        @readfile($mainFile);

        /**
         * Now delete the zip file. IF you want to store it then you can. just remove this line.
         */
        unlink($mainFile);
    
    }

}
add_action('wp_loaded', 'vdm_files_downloads');