Ok thx for the answer, i have changed the code
function my_project_updated_send_email( $post_id ) {
// If this is just a revision, don't send the email.
if ( wp_is_post_revision( $post_id ) )
return;
$to = $author ;
$post_title = get_the_title( $post_id );
$post_url = get_permalink( $post_id );
$subject = 'A post has been updated';
$message = "A post has been updated on your website:\n\n";
$message .= $post_title . ": " . $post_url;
// Send email to admin.
wp_mail( example@example.com, $subject, $message );
}
add_action( 'save_post', 'my_project_updated_send_email' );
This work to,, but i need to send the mail to the Author of the post, can some one explain me the corret code pls?