How to share same post to multiple site in wordpress?

We are developing WordPress with multiple site. We need to share some posts to more than one site. We need to save post in more than one sites with a single click.

I have searched in Google, but I can’t get any tutorial for that.

You can use the function switch_to_blog() for this

$other_id = 1234 // the id of the other blog to save the post to
switch_to_blog($other_id);
$my_post = array(
  'post_title'    => $post_title,
  'post_content'  => $post_content,
  'post_status'   => 'publish',
  'post_author'   => $post_author,
  );

// Insert the post into the database
wp_insert_post( $my_post );

restore_current_blog();

There is a pitfall if you execute this code on the save_post hook, because wp_insert_post also calls save_post and you end up in an infinite loop. This post on Stack Overflow gives a solution for that.