构建WP\\u User\\u查询时，您的思路是正确的，但您没有使用此查询的结果。请参见：

 //verify post is not a revision 
if ( !wp_is_post_revision( $post_id ) ) { 

        //gets subscirbers to send email to
        // WP_User_Query arguments
        $args = array (
            \'role\'           => \'Subscriber\',
        );


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

        // get email addresses from user objects
         $email_addresses = array();
        foreach ( $user_query->results as $user ) {
            $email_addresses[] = $user->user_email;
        }

        // build message
        $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 .= "<a href=\'". $post_url. "\'>" .$post_title. "</a>\\n\\n"; 

        //send email to all emails
        wp_mail($email_addresses, $subject, $message );

}

你就快到了，但实际上你没有从你的User Query

此代码应该满足您的要求，但是，如果我对您的问题理解正确，您希望向每个订阅者发送一封单独的电子邮件，这是没有效率的。

最好将所有电子邮件地址添加到一个数组中，并一次性发送电子邮件（即wp_mail 函数将为您正确分隔它们）。更好的是，将地址添加到密件抄送字段，这样您的订阅者将无法看到所有其他订阅者的地址。

add_action(\'publish_post\', \'vb_esa_update_email\'); 
function vb_esa_update_email($post_id){ 

    /** Ensure that the post is not a revision */
    if(wp_is_post_revision($post_id)) :
        return;

    /** Query all users who have the role \'Subscriber\' */
    $args = array (
        \'role\'           => \'Subscriber\',
    );
    $user_query = new WP_User_Query($args);

    /** Check to see if there are any matching users */
    if(!empty($user_query->results)) : 

        /** Set up the email subject and message */
        $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.= "<a href=\'". $post_url. "\'>" .$post_title. "</a>\\n\\n"; 

        /** Send an individual message to each user */
        foreach($user_query->results as $user) :

            wp_mail($user->data->user_email, $subject, $message);

        endforeach;

    endif;

}

这是一个answer to a similar question 这可能会有所帮助。您应该调整上述答案中的代码，以选择具有角色的用户subscriber.