Create a Cron job after every post publish - wordpress

Question

I have a situation where i want to create a cron job after every WordPress blog post publish. Cron job will run after 7 days of publishing post and check if all the users have viewed the posts and email the list of not viewed post by users list. How can i achieve this. Its a WordPress website and there are around 300+ users, after each blog post publish user gets notification. So want to check who has viewed and who has not viewed the post.

Answer 1

If you want to start the cron job only the first time a post is published, you'll want to use the draft_to_publish hook.
draft_to_publish

Answer 2

Well there are Plugins capable of managing Stats and tracking users activities. I'm not sure which one fit to your needs but I'll try to give a simple approach to do it by yourself.
Tracking
We can set a custom field for those (posts/post-types) where we will store a list of users who read that post. Let's call it readerslist
On the single.php file we will add these lines to Update this field.
$list = explode(',',get_post_meta($post->ID, 'readerslist', true));
$user = get_current_user_id();
if (!in_array($user,$list)){
array_push($list, $user);
update_post_meta( $post->ID, 'readerslist', implode(",", $list) );
}
Now that we can retrieve who viewed the article? We could later find those who didn't read it yet.
Then in functions.php we could set up a hook that will execute when a post get published, to set a single scheduled cron job to send the absent readers.
<?php
function wpdocs_run_on_publish_only( $new_status, $old_status, $post ) {
{
if ($new_status != 'publish') {
return;
}
//You better add limitations to choose specific post_types you are targeting
$postid=$post->ID;
add_cron($postid);
}
add_action( 'transition_post_status', 'wpdocs_run_on_publish_only', 10, 3 );
function add_cron($postid){
$nxtweek = strtotime("+1 week");
add_action('sendemail', 'stats_mail', 10, 1);
wp_schedule_single_event(time() + $nxtweek, 'sendemail',array( $postid);
}
function stats_mail($postid)
{
$readerslist = get_post_meta( $postid, 'readerslist', true );
$users = get_users( array( 'fields' => array( 'ID' ) ) );
$absents = array_diff($users, explode(",",$readerslist));
//Now that you got the list of absent users
$names='';
foreach ($absents as $x){
$names.=$x.' : '.get_user_meta( $x,'first_name' , true ).' '.get_user_meta( $x,'last_name' , true ).'<br>';
}
$title=get_the_title($postid);
$to = 'you#example.com';
$subject = 'Users who didn\'t read '.$title;
$headers = array('Content-Type: text/html; charset=UTF-8');
wp_mail( $to, $subject, $names, $headers );
}
?>
Notice : I didn't tested the above code ! I made you this in order to show you how to do it. But there isn't much work to do here. Good luck

Answer 3

I tried your code, it works fine, but i am not able to make it working as i wanted, can you look into it. I don't know what i am doing wrong.
function wpdocs_run_on_publish_only( $new_status, $old_status, $post ) {
if ($new_status != 'publish') {
return;
}
$postid=$post->ID;
add_cron($postid);
}
add_action( 'transition_post_status', 'wpdocs_run_on_publish_only', 10, 3 );
function add_cron($postid){
$nxtweek = strtotime("+1 week");
add_action('sendemail', 'stats_mail', 10, 1);
if ( ! wp_next_scheduled( 'sendemail') ) {
wp_schedule_event(time() + $nxtweek, $nxtweek, 'sendemail', array($postid));
// i want to run cron every 7 days from the date of publishing post, until all user reads it, i tried this code but not working.
// wp_mail( 'email#company.com', $postid, 'test', null );
// For testing purpose if i send mail from here, it goes.
}
}
function stats_mail($postid) {
wp_mail( 'email#company.com', $postid, 'test', null );
// this doesnt work.
$readerslist = get_post_meta( $postid, 'readerslist', true );
$users = get_users( array( 'fields' => array( 'ID' ) ) );
$absents = array_diff($users, explode(",",$readerslist));
//Now that you got the list of absent users
$names='';
foreach ($absents as $x){
$names.=$x.' : '.get_user_meta( $x,'first_name' , true ).' '.get_user_meta( $x,'last_name' , true ).'<br>';
}
$title=get_the_title($postid);
$to = 'email#company.com';
$subject = 'Users who didn\'t read '.$title;
$headers = array('Content-Type: text/html; charset=UTF-8');
//wp_mail( $to, $subject, $names, $headers );
}