Search content for shortcodes and get parameters

This is working for me

  $shortcode="book";
  $pattern = get_shortcode_regex();

  // if shortcode 'book' exists
  if ( preg_match_all( "https://wordpress.stackexchange.com/". $pattern .'/s', $post->post_content, $matches )
    && array_key_exists( 2, $matches )
    && in_array( $shortcode, $matches[2] ) )  {
   $shortcode_atts = array_keys($matches[2], $shortcode);

 // if shortcode has attributes
 if (!empty($shortcode_atts)) {
  foreach($shortcode_atts as $att) {
    preg_match('/id="(\d+)"https://wordpress.stackexchange.com/", $matches[3][$att], $book_id);

    // fill the id into main array
    $book_ids[] = $book_id[1];
  }
}
...