How can I implement a notification system in wordpress?

Question

I have to send a Firebase Cloud Message (FCM) to an android application when a new post is inserted in a wordpress blog, I already put my code in the wp_includes\post.php , but this will not work, cause of the future WP update(post.php will be replaced and I can't insert my code evry time), so I have to put my code(it works no problem in this) in another place.. where I can put my file?? I have to write a plugin? It's possible to write a plugin that override a function? in this case wp_insert_post? And if this is possible where i retrieve the post data to send via FCM? Can you make an example or link a good example of code if this is possible?

Now my code is inside the wp_insert_post function and so it's executed when you push the button "publish" in new post area.

Answer 1

If you look through the definition of wp_insert_post(), you'll see

do_action( 'wp_insert_post', $post_ID, $post, $update );

at the end of it. So you can hook into this and perform whatever task you want to after creating a post.

Something like this in your theme's functions.php or in your plugin file:

do_action( 'wp_insert_post', 'send_notification');
function send_notification($post_ID, $post, $update){
    //your code here
}