/**
     * Save a base64 jpeg image on the server in Media library.
     */
    function save_image($base64_image_string, $output_file_name_without_extension) {
      global $wp_filesystem;
      // Initialize the WP filesystem, no more using 'file-put-contents' function
      if (empty($wp_filesystem)) {
        require_once (ABSPATH . '/wp-admin/includes/file.php');
        WP_Filesystem();
      }
      // get uploads dir
      $upload_dir = wp_upload_dir();
      $upload_basedir = $upload_dir['basedir'];
      $upload_baseurl = $upload_dir['baseurl'];
      $screens_dir = $upload_basedir . '/flo_forms_screens/'; // custom folder where the screen shots will be kept
      // if folder that will hold the screens does not exist yet, create it
      if(!$wp_filesystem->is_dir($screens_dir)) {
        $wp_filesystem->mkdir($screens_dir);
      }
      // folder exists, push image to it
      $file = false;
      if($wp_filesystem->is_dir($screens_dir)) {
        $img             = str_replace( 'data:image/jpeg;base64,', '', $base64_image_string );
        $img             = str_replace( ' ', '+', $img );
        $decoded         = base64_decode( $img );
        $hashed_filename = md5( $output_file_name_without_extension . microtime() ) . '_' . $output_file_name_without_extension;
        $filePath = $screens_dir . $hashed_filename . ".jpeg";
        $fileCallback = $wp_filesystem->put_contents(
          $filePath,
          $decoded,
          FS_CHMOD_FILE // predefined mode settings for WP files
        );
        $publicFilePath = str_replace($upload_basedir, $upload_baseurl, $filePath);
        if($fileCallback) $file = $publicFilePath;
      }
      return $file;
    }