trigger email when post is published by someone a user follows

Question

I'm trying to send an email to all users who are following a certain post author when they publish a post. I have this function below, but does not seem to work. a few notes

the meta value = 'following' is an array that contains the authors user follows.

function followerPost_notification($post_id) {

$post = get_post($post_id);
$uid = $post->post_author;
$user_info = get_userdata($post->post_author);
$email = $user_info->user_email;
$first_name = $user_info->first_name;
$pTitle = $post->post_title;
$pUrl = get_permalink($post_id);

//Email Info
$subject = 'New Post Published by a Person you Follow!' ;
$headers[] = 'Content-Type: text/html; charset=UTF-8';

// WP_User_Query arguments
$args = array (
    'meta_query
    '     => array(
        array(
            'key'   => 'following',

        ),
    ),
);

// The User Query
$user_query = new WP_User_Query( $args );

$q = $user_query->results;
// The User Loop
if ( ! empty( $user_query->results ) ) {
    foreach ( $user_query->results as $user ) {
        $uid2 = $user->ID;
        $uemail = $user->user_email;
        $to = $uemail;
        $meta= get_user_meta($uid2,'following', true);
        $arr = implode(',', $meta);

    if(strpos($uid, $arr)) {

    ob_start(); 

include("template/email_header.php");
?>
<p>New post published by a person you follow</p>

<p><em>This is an automated email, please don't reply to this email.</em></p>
<?php 
include("template/email_footer.php");

    $message = ob_get_contents();
ob_end_clean();

wp_mail( $to, $subject, $message, $headers );

    }

    }
} else {
    // no users found
}

}
add_action('publish_post', 'followerPost_notification');

Answer 1

Was able to figure out that the meta value was being stored as a string, which doesn't play nice with the meta query.

So what I had to do was do a like comparison with the serialized string version of my meta value. The meta query ended up like this

$args = array (
    'meta_query'     => array(
        array(
            'key'   => 'following',
            'value'   => serialize( strval( $uid ) ),
            'compare'   => 'LIKE',

        )
    )
);

for more insght, check out this other post that helped me

How can I create a meta_query with an array as meta_field?