How to Send SMS Notifications to Readers When New WordPress Posts are Published

Time to read: 4 minutes

June 29, 2017
Written by
Alex Swan
Contributor
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Make sure your subscribers see every post by offering instant SMS notifications when you publish new blog posts in WordPress.

At the end of this project, you will have a custom WordPress Plugin that allows:

1. WordPress users to have a “Mobile Phone” field in their profile to sign up for notifications
2. posts to automatically send a notification message to every subscriber who signs up

If you’re in a hurry, you can find the almost-ready code on GitHub, just drop in the latest Twilio PHP Library and update your Twilio variables in sms-notify.php.

Setup

You will need to already have a WordPress Blog running to build this plugin.

In your WordPress directory, go to wp-content/plugins and make a directory called sms-notify. Inside that directory, make a file named sms-notify.php. In this file we’ll start with some plugin metadata. This is what WordPress reads to show in our Plugin Dashboard. 

<?php
/**
 * @package SMS_Notify
 * @version 1.0
 */
/*
Plugin Name: SMS Notify
Description: This has two functions. First, it adds a 'mobile' field to users' profiles, along with a 'notifications' check box. Second, it adds a hook to send an SMS to each user when a post is published.
Author: Alex Swan
Version: 1.0
Author URI: http://bold-it.com/
*/

// Our code will go here

?>

Next, activate our new plugin. Go to your WordPress Dashboard at the “/wp-admin” path and click the Plugins link on the left column. Click the “Activate” link on our plugin called SMS Notify.

Activate our SMS Notify plugin

Once it’s active, the link will say “Deactivate”. If something went wrong, you’ll see an error. Time to start modifying WordPress!

Let Users Store Their Phone Number

We want users to be able to sign up for SMS notifications, and we’ll do that by adding a phone field in their user profile. WordPress makes this easy with the user_contactmethods function. Add this code to sms-notify.php: 

function modify_contact_methods ($profile_fields) {
    $profile_fields['mobile'] = "Mobile Phone (12223334444)";

    return $profile_fields;
}
add_filter('user_contactmethods','modify_contact_methods');

When WordPress shows the user_contactmethods data, it will now pass it to our function before going on to display it to the user. We add the mobile field to it so our user can put their phone number in it. Let’s try it out!

Back at the “/wp-admin” path, go to the Users tab and click the Add User button. Create a user with the role Subscriber. In an incognito window, log in to your blog with that user’s credentials, then go to “/wp-admin/profile.php”. Add a phone number for your new user, then hit Save.

Save a phone number

If This Action Happens, Then Send an SMS

Create an Action Hook

Next, set up a function that is invoked during a publish_post action and use get_users to iterate over all the subscribers of the blog. This code is in preparation for sending a text message to each subscriber with a number attached to their profile.

function post_published_notification ( $ID, $post ) {
    // TODO: Prepare Twilio stuff here

    $title = $post->post_title;
    $body = sprintf('New Post: %s', $title);

    $blogusers = get_users( 'blogid=$ID&role=subscriber' );
    foreach ( $blogusers as $user ) {
        $to = get_user_meta($user->ID, 'mobile', true);
        if ( intval($to) == 0 ) { continue; }
        // TODO: Send a text message
    }
}
add_action('publish_post', 'post_published_notification', 10, 2);

For each of the blog’s Subscribers, WordPress gets the phone number stored using get_user_meta. Finally, add_action gets configured to execute post_published_notification when the publish_post action happens. Now, to send our SMS.

Set Up Your Twilio Account

Go to the Twilio Console (sign up for a free account if you do not already have one) and note your Account SID, Auth Token and a phone number you purchase. You’ll need to add this information in next.

Use Twilio to Send an SMS

Go to Twilio’s PHP Library and install the library. It’s recommended to use Composer, but copying the twilio-php-master folder into our sms-notify folder works as well. Now add references to the library in the top of sms-notify.php (after the metadata). 

require __DIR__ . '/twilio-php-master/Twilio/autoload.php';
use Twilio\Rest\Client;

Modify our post_published_notification function to make a Twilio client, and send a message in the foreach loop. 

function post_published_notification ( $ID, $post ) {
    // Your Account SID and Auth Token from twilio.com/console
    $sid = 'ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX';
    $token = 'auth_token_here';
    // A Twilio phone number you purchased at twilio.com/console
    $from = "+15555550199";
    $client = new Client($sid, $token);

    $title = $post->post_title;
    $body = sprintf('New Post: %s', $title);

    $blogusers = get_users( 'blogid=$ID&role=subscriber' );
    foreach ( $blogusers as $user ) {
        $to = get_user_meta($user->ID, 'mobile', true);
        if ( intval($to) == 0 ) { continue; }
        $client->messages->create(
            $to,
            array(
                'from' => $from,
                'body' => $body
            )
        );
    }
}
add_action('publish_post', 'post_published_notification', 10, 2);

Be sure to update the $sid, $token, and $from variables to your own Account SID, Auth Token and a Twilio phone number that you own.

Test

Head back to your WordPress admin page at “/wp-admin” and add a new post. Write your deepest desires, then hit the publish button.

That’s it! We got our SMS notification that a new post has been published.

What’s Next

Now that basic functionality is done, you can use this as a springboard for your own ideas. Here are a few ways to build on this project:

Thanks for using this code to enable SMS notifications on newly-published WordPress posts. Let me know what you build by contacting me via boldbigflank on GitHub or @boldbigflank on Twitter.

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