One of the main components of every web application is the ability to send emails.

Now, this doesn't mean that every web application is its own mail client (although people do create their own mail clients).

Instead, what I mean is that when a user registers, when a user changes their password, when something in the system changes, or more generally, whenever something happens that the website owner wants to notify the user, the application Usually an email will be sent.

So far in this series, we’ve covered:

• User Management
• Permissions
• Session Management

The previous article is arguably one of the most complex we will cover; however, it is necessary for those looking to add more advanced features to their projects.

With that said, we’re going to take a break from some of the more complex material and look at what WordPress has to offer when it comes to sending emails.

Understanding email

Before we dive into what the WordPress API offers in terms of sending emails, customizing emails, and more, it’s important to know a few things about email.

That said, it’s important to understand the components that go into creating an actual email—after all, it’s more than just an address, subject, and content.

Before we start building our own custom email, there are some technical nuances worth understanding.

title

In short, email headers contain a minimal set of information, including: who sent the email and the address from which the email was sent.

Typically, you may see additional information included in the header. For example, this information might include the timestamp when the email was sent.

For WordPress, the sender specified in the email header is always defined as the default sender in WordPress unless otherwise specified.

For example, if you wish to set the reply address to "donotreply@domain.com", then you must customize this.

Additionally, it's usually best to use email headers in the form of an array so that you can easily construct, specify, and pass addresses, CC addresses, and BCC recipients.

MIME Type

When it comes to the format that emails follow, you may see two forms:

• Plain Text
• HTML

You're used to seeing HTML in most modern email clients; however, if you have a simpler client, set it up to display only plain text, or you're reading email on a slightly older phone mail, you will read the content as plain text.

WordPress can send emails as plain text or HTML.

We'll see exactly how to do this when we look at an example of how to send an email programmatically. In short, there's a hook that makes it really easy - but we'll wait to see it in action until we cover the rest of the necessary parts of the email.

appendix

As you know, an attachment is actually any file that you attach to an email and send to the recipient.

The thing is, there are some rules that govern email - but they're not necessarily set by the software. Instead, servers, email clients, and various other rules limit what we can receive in our inboxes.

For example:

• Some clients do not allow sending zip files or executable files
• Many email services have limits on the maximum file size that can be attached
• Certain types of emails may be marked as spam based on their attachments (or their content)

Regardless, this is beyond our control - we just need to know the limits on who we email and make sure we adhere to them.

To do this, it’s very easy to create attachments to send via WordPress emails.

While attachments are obviously not required, you may want to attach a single file or even multiple files. In WordPress, this can be done via a string or an array.

We won't see exactly how to do this right now, but when we look at an example of how to send an email programmatically, we will understand it immediately.

Recipients, Subjects and Messages

At the most basic level, each email contains a "To" email address, a "Subject" and a "Message" ".

In WordPress, these settings are also very easy - just provide a string for each setting and you are good to go.

Of course, if you want to send an email to multiple people, you can iterate over the address collection and send an email to each user, Alternatively, you can provide WordPress with a set of recipients mail API , which will send the email to everyone included.

Remember: If you want to specify a different reply-to address, please specify it in the header we covered earlier in this article.

Using WordPress Email API

With all that said, we’re ready to take a hands-on look at the WordPress Email API.

In short, all functionality is contained in a single function called wp_mail; however, if we want to take full advantage of what this application has to offer, there are some we Things to note.

Required hooks

Specifically, we will use the following hooks:

• wp_mail_content_type Allows us to define the MIME type of the email being sent
• wp_mail_from is a filter that we can use to define the sender address instead of using the $headers array
• wp_mail_from_name is a filter that we can use to define the sender of this person instead of using the $headers array
• wp_login is the hook we use for the demo so that every time someone logs into the WordPress dashboard we will send an email to someone

For the sake of completeness, I'll share the entire code below and then we'll walk through it.

source code

<?php
function acme_email_individual( $input ) {

	/**
	 * Note: assume that $input has keys for 'email-address'.
	 */

	// Generate the password
	$password = wp_generate_password ( 12, false );

	// Email the user that they're profile was created
	$message = 'Hey There,';
	$message .= '<br /><br />';
	$message .= 'Your account has been created. Your login information is below:';
	$message .= '<br />';
	$message .= '<ul>';
		$message .= '<li>Username: ' . $input['email-address'] . '</li>';
		$message .= '<li>Password: ' . $password . '</li>';
	$message .= '</ul>';
	$message .= '<br />';
	$message .= 'You can login to the application <a href="' . get_bloginfo( 'siteurl' ) . '">here</a>.';

	add_filter( 'wp_mail_content_type', create_function( '', 'return "text/html";' ) );
	add_filter( 'wp_mail_from', 'acme_mail_from' );
	add_filter( 'wp_mail_from_name', 'acme_mail_from_name' );
	wp_mail( $input['email-address'], 'Your Acme Account Has Been Created!', $message, array() );

}

function acme_mail_from( $email ) {
	// NOTE: replace [at] with @. This was causing problems with the syntax highlighter.
	return 'donotreply[at]acme.com';
}

function acme_mail_from_name( $name ) {
	return 'The Acme Company';
}

If you've been reading this article so far, none of this is too surprising: after all, we're leveraging hooks provided by WordPress, we're building strings to pass as function arguments, and then we call wp_mail function.

Note, however, that we pass an empty array as the $headers parameter for this email. This is because we use custom filters to set "Sender Name" and "Sender Address", using filters and hook functions instead of arrays.

This way is not necessarily better than others; however, its purpose is to demonstrate that there are multiple ways to achieve the same result.

Now, onto the data!

This is another feature of WordPress that allows you to easily include email functionality into your web application.

In fact, I think WordPress' event model makes it incredibly easy to introduce email functionality in any imaginable scenario - just send an email if there's a hook available.

With that said, it’s time to turn our attention to one of the most common aspects of web application development: data management.

Specifically, we need to study how to save information to the database and retrieve information from the data, and how to complete these operations safely and efficiently.

So, starting with the next article, we will do just that.