Automation on Post Publish | https://www.ibenic.com/automation-post-publish

cron.php

 <?php

add_action( 'publish_future_post', 'automation_on_publish', 20, 1 );

/**
 * Create automate tasks on post publish.
 * 
 * @param integer $post_id Post ID that is published.
 */
function automation_on_publish( $post_id ) {
  $post = get_post( $post_id );
        
  if ( empty( $post ) ) { return; }
  
  // Let's be sure that we are checking against our post type.
  if ( 'our_post_type' !== get_post_type( $post ) ) { return; }
  
  // This post has probably been published already.
  if ( 'future' != $post->post_status && 'publish' != $post->post_status) { return; }

  $time = strtotime( $post->post_date_gmt . ' GMT' );

  // Nope, we still won't run. WP will reschedule it so we're fine.
  if ( $time > time() ) {
      return;
  }
  
  // let's do something on the automation. 
  
  // or just create a hook so we can be sure when hooking that we're be fine.
  do_action( 'automation_on_publish', $post );
}

hook.php

<?php

add_action( 'transition_post_status', 'automation_on_post_status', 10, 3 );

/**
 * Automating on general hook.
 */
function automation_on_post_status( $new_status, $old_status, $post ) {
  if ( 'publish' === $new_status && 'future' === $old_status ) {
     // Do something if the post has been transitioned from the future (scheduled) post to publish.
  }
}

hook2.php

<?php

add_action( 'future_to_publish', 'automation_on_future_to_publish' );

/**
 * Automating on specific status change.
 */
function automation_on_future_to_publish( $post ) {
  // We are sure that the post has been published from scheduled status.
}

hook3.php

<?php

add_action( 'publish_my_post_type', 'automation_on_publish', 10, 2 );

/**
 * Automating on publish for post type.
 */
function automation_on_publish( $post_id, $post ) {
  // We are sure that our post type has been published.
}

wp-transition.php

<?php

// wp-includes/post.php
function wp_transition_post_status( $new_status, $old_status, $post ) {
	/**
	 * Fires when a post is transitioned from one status to another.
	 */
	do_action( 'transition_post_status', $new_status, $old_status, $post );

	/**
	 * Fires when a post is transitioned from one status to another.
	 */
	do_action( "{$old_status}_to_{$new_status}", $post );

	/**
	 * Fires when a post is transitioned from one status to another.
	 */
	do_action( "{$new_status}_{$post->post_type}", $post->ID, $post );
}

wp.php

<?php
// wp-includes/default-filters.php
add_action( 'publish_future_post', 'check_and_publish_future_post',   10, 1 );

// wp-includes/post.php
/**
 * Publish future post and make sure post ID has future post status.
 *
 * Invoked by cron 'publish_future_post' event. This safeguard prevents cron
 * from publishing drafts, etc.
 *
 * @since 2.5.0
 *
 * @param int|WP_Post $post_id Post ID or post object.
 */
function check_and_publish_future_post( $post_id ) {
	$post = get_post($post_id);

	if ( empty($post) )
		return;

	if ( 'future' != $post->post_status )
		return;

	$time = strtotime( $post->post_date_gmt . ' GMT' );

	// Uh oh, someone jumped the gun!
	if ( $time > time() ) {
		wp_clear_scheduled_hook( 'publish_future_post', array( $post_id ) ); // clear anything else in the system
		wp_schedule_single_event( $time, 'publish_future_post', array( $post_id ) );
		return;
	}

	// wp_publish_post() returns no meaningful value.
	wp_publish_post( $post_id );
}