How to use?
API docs
WordPress functions
Get API key
Create a request
Pass args
Process response
Examples
Get subscribers count
Get all emails from a list
Subscribe or unsubscribe a email
Delete list members
Batches

Mailchimp API in WordPress

Updated on August 20, 2022

In this tutorial we are going to talk deeply about establishing connection with Mailchimp API using WordPress HTTP API functions.

In our code examples we are going to use wp_remote_get(), wp_remote_post() and wp_remote_request() functions. If you’re looking for cURL examples, here is another tutorial.

In 2016 I developed Simple Mailchimp Sync plugin that allows to sync your WordPress users with specific Mailchimp audiences. I continue supporting and developing this plugin. So, I have some experience with Mailchimp API guys.

How to Use Mailchimp API in WordPress?

Before we dive into actual examples, let’s figure out some basics.

Mailchimp APIs

First things first, Mailchimp Marketing API is available by this link. There is also transactional API, here is the link.

What WordPress HTTP API function to use?

Second, we have to figure out what WordPress HTTP API function we have to use for our specific task. As I mentioned before, there are three of them – wp_remote_get(), wp_remote_post() and wp_remote_request(). Actually you can use any of them for any request, but in order to make our code more beautiful and clear, we are going to use wp_remote_get() for GET requests, wp_remote_post() – for POST requests and wp_remote_request() for PUT, PATCH and DELETE requests.

Let’s take a look at the screenshot.

Where to get Mailchimp API key?

For every API request we will need an API key. I already described where you can get it here.

Create a HTTP API request

Now let’s use a screenshot above and create a request. Let’s begin with the simplest one.

$response = wp_remote_get( 
	'https://'. substr($api,strpos($api,'-')+1) . '.api.mailchimp.com/3.0/lists/', 
	array(
 		'headers' => array(
			'Authorization' => 'Basic ' . base64_encode( 'user:'. $api )
		)
	)
);

Some moments I would like to highlight in this code:

In every example $api variable is our API key we should specify before in the code.
As you can see API key is used not only for basic authorization, but also as part of a request URL, so your URL will start with something like https://us14.api.mailchimp.com... or https://us5.api.mailchimp... etc.

Pass parameters to a HTTP request

If you check the documentation of /lists, you can find out that by default it returns only the last 10 audiences. But what if you need more? Let’s for example get at least 100 audiences per request? So we have to specify it in count parameter (according to API docs). Parameters can be passed in the body of the request as a JSON-encoded array.

$response = wp_remote_get( 
	'https://'. substr($api,strpos($api,'-')+1) . '.api.mailchimp.com/3.0/lists/', 
	array(
 		'headers' => array(
			'Authorization' => 'Basic ' . base64_encode( 'user:'. $api )
		),
		'body' => json_encode( 
			array(
    			'count' => 100
			)
		)
	)
);

Process the response data

Once the request has been made, the main work is usually finished – maybe a specific email is subscribed to a specific audience, maybe a specific audience has been removed – I don’t know what you’re doing. But usually we have to get the information about the finished request. In our case – we are going to print the Mailchimp audiences as an <ul> list.

WordPress functions wp_remote_retrieve_response_code(), wp_remote_retrieve_body(), wp_remote_retrieve_response_message() are intended to help us. It is not 100% necessary to use any of them actually. You can print_r( $response ) and you will find out why. But I prefer to use them in order to make my code clean and readable.

Direct usage	WordPress function
`$response['response']['code']`	`wp_remote_retrieve_response_code( $response )`
`$response['body']`	`wp_remote_retrieve_body( $response )`
`$response['response']['message']`	`wp_remote_retrieve_response_message( $response )`

Example:

if( 'OK' === wp_remote_retrieve_response_message( $response ) ) {
// if( 200 === wp_remote_retrieve_response_code( $response ) ) {
	$body = json_decode( wp_remote_retrieve_body( $response ) );
	if( $body->lists ) {
		echo '<ul>';
		foreach( $body->lists as $list ) {
			echo "<li>{$list->name} ({$list->stats->member_count})</li>";
		}
		echo '</ul>';
	}
} else {
	echo 'The request failed.';	
}

Mailchimp API Examples

Get list subscribers count

In this example we will get all the information about a specific audience (list) in Mailchimp and its subscribers count. You will also need an audience ID, how to get it I described here.

$list_id = 'YOUR AUDIENCE ID';

$response = wp_remote_get( 
	'https://' . substr($api,strpos($api,'-')+1) . '.api.mailchimp.com/3.0/lists/' . $list_id,
	array(
	 	'headers' => array(
			'Authorization' => 'Basic ' . base64_encode( 'user:'. $api )
		)
	)
);

if ( 200 == wp_remote_retrieve_response_code( $response ) ) {
	$body = json_decode( wp_remote_retrieve_body( $response ) );
	echo 'Subscribers:' . $body->stats->member_count;
}

Get all subscriber emails from a specific audience

We continue to work with GET requests, so we’re still using wp_remote_get() function.

$list_id = 'YOUR AUDIENCE ID';

$response = wp_remote_get( 
	'https://' . substr($api,strpos($api,'-')+1) . '.api.mailchimp.com/3.0/lists/' . $list_id . '/members/', 
	array(
	 	'headers' => array(
			'Authorization' => 'Basic ' . base64_encode( 'user:'. $api )
		)
	)
);

if( 200 === wp_remote_retrieve_response_code( $response ) ) {
	$emails = array();
	$body = json_decode( wp_remote_retrieve_body( $response ) );
	foreach( $body->members as $member ) {
		if( 'subscribed' !== $member->status ) {
			continue;
		}
		$emails[] = $member->email_address;
	}
	print_r( $emails );
}

$list_id = 'YOUR AUDIENCE ID';

$response = wp_remote_request( 
	'https://' . substr($api,strpos($api,'-')+1) . '.api.mailchimp.com/3.0/lists/' . $list_id . '/members/' . md5(strtolower($email)),
	array(
		'method' => 'PUT',
	 	'headers' => array(
			'Authorization' => 'Basic ' . base64_encode( 'user:'. $api )
		),
		'body' => json_encode(
			array(
				'email_address' => 'no-reply@rudrastyh.com', // change the email here
				'status' => 'subscribed' // unsubscribed, pending
			)
		)
	)
);

if( 'OK' === wp_remote_retrieve_response_message( $response ) ) {
	echo 'The user has been successfully subscribed.';
}

Delete list members

If you want just to set status unsubscribed or cleaned for you subscriber – look at the previous example. But if you want to completely remove a specific user email from a list, this code is for you then:

wp_remote_request(
	'https://' . substr($api,strpos($api,'-')+1) . '.api.mailchimp.com/3.0/lists/' . $list_id . '/members/' . md5(strtolower($email)),
	array(
		'method' => 'DELETE',
	 	'headers' => array(
			'Authorization' => 'Basic ' . base64_encode( 'user:'. $api )
		)
	)
);

Batch subscribe all users with a specific role

There are not much examples of Mailchimp batch operations over the internet, but your can find another one on this website here.

// "Schema describes object"? Not a problem
$args = new stdClass();
// all the batch operations will be stored in this array
$args->operations = array();
 
$users = get_users( 'role=subscriber' );
if( $users ) {
	foreach( $users as $user ) {
		// a single batch operation object for each user
		$batch = new stdClass();
		$batch->method = 'PUT';
		$batch->path = 'lists/' . $list_id . '/members/' . md5(strtolower($user->user_email));
		$batch->body = json_encode( 
			array(
				'email_address' => $user->user_email,
				'status'        => 'subscribed',
				'merge_fields'  => array( 
					'FNAME' => $user->first_name,
					'LNAME' => $user->last_name
				)
			)
		);
		$args->operations[] = $batch;
	}
}

$response = wp_remote_post( 
	'https://' . substr($api,strpos($api,'-')+1) . '.api.mailchimp.com/3.0/batches', 
	array(
		'method' => 'POST',
	 	'headers' => array(
			'Authorization' => 'Basic ' . base64_encode( 'user:'. $api )
		),
		'body' => json_encode( $body_args )
	)
);

$body = json_decode( wp_remote_retrieve_body( $response ) );
echo $body->id;

$body->id is the batch operation ID, try to get a status of a batch operation by yourself using wp_remote_get() and this API endpoint /batches/{batch_id}.

# Mailchimp, WordPress

Misha Rudrastyh

Hey guys and welcome to my website. For more than 10 years I've been doing my best to share with you some superb WordPress guides and tips for free.

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Comments — 7

Ripul Jul 14, 2016

I was just wondering when WordPress supports HTTP API MailChimp API can be implemented using it.
Thanks for sharing this.

Tom

Jun 4, 2018

Again, your code save me!
However I tried to send order details according to Mailchimp API adapting your code in this way:

$api_key = xxx;
$list_id = xxx;

$order = array(
'headers' => array('Authorization' => 'Basic ' . base64_encode( 'user:'. $api_key )),
'body' => json_encode(array(
	'id' => 'order_453645',
	'customer' => array(
		'id' => 'user_307' ),
	'currency_code' => 'EUR',
	'order_total' => 99,
	'lines' => array(
		'id' => 'line_989',
		'product_id' => 'product_93',
		'product_variant_id' => 'product_4014',
		'quantity' => 1,
		'price' => 99)
	))
);
		
$response = wp_remote_post( 'https://us18.api.mailchimp.com/3.0/ecommerce/stores/. $list_id ./orders', $order );
$body = json_decode( $response['body'] );

But it doesn’t work.. I successfully add members, customers, stores and lists to Mailchimp but there’s no chance to send order details. Do you see something wrong in this code?
Thanks!

Misha

Jun 5, 2018

Hey Tom,

First, $list_id variable is your store_id, right?
Second, you forgot the quotes:

$response = wp_remote_post( 'https://us18.api.mailchimp.com/3.0/ecommerce/stores/' . $list_id . '/orders', $order );

Third, where is 'method'=>'POST' parameter?

Try to print_r( $response ) and check out what is inside it.

Thanks for your reply Misha,
sorry for the typo: $list_id is my $store_id
I added the method POST parameter.
Customer id “user_307” is an existing user and product_id / product_variant_id is an existing product (I checked with a GET request), as well as store and list: created and working on Mailchimp.

With this code I successfully create new customers, add members and create store but no luck with orders (update code):

$api_key = xxx;

$order = array(
'method' => 'POST',
'headers' => array('Authorization' => 'Basic ' . base64_encode( 'user:'. $api_key )),

'body' => json_encode(array(

	'id' => 'order_453645',
	'customer' => array(
		'id' => 'user_307' ),
	'currency_code' => 'EUR',
	'order_total' => 99,
	
	'lines' => array(
		'id' => 'line_989',
		'product_id' => 'product_93',
		'product_title' => 'Product 1',
		'product_variant_id' => 'product_4014',
		'product_variant_title' => 'medium',
		'quantity' => 1,
		'price' => 99
	)
	
	))
);
$response = wp_remote_post( 'https://us18.api.mailchimp.com/3.0/ecommerce/stores/stxxxx_1/orders/', $order );
$body = json_decode( $response['body'] );
}

Misha Jun 7, 2018

Hi Tom,

customer must be object, not array.

AKumar Jun 18, 2023

WordPress HTTP API functions and WordPress Rest API are two different things?

- Misha Jun 18, 2023
  
  Yep