Mailchimp 3.0 API Calls

/*
 * Mailchimp API Calls
 * V. 3.0
 */
 
//Push users to mailchimp on GF form completion
function mailchimp_newsletter_push_form_8($entry, $form) {

	$list_id = '';
	$email = $entry[3];
	
	$subscriber = mailchimp_get_subscriber( $list_id, $email );

	// If subscriber does not exist, create one.
	if ( ! isset( $subscriber['id'] ) ) {

		$subscriber = array();
		$subscriber['status'] = "subscribed";
		$subscriber['email_address'] = $email;
		$subscriber['list_id'] = $list_id;

	} else {
		$subscriber['status'] = "subscribed";
	}

	$response = mailchimp_update_subscriber( $list_id, $email, $subscriber );
}
add_action( 'gform_after_submission_8', 'mailchimp_newsletter_push_form_8', 10, 2 );

function mailchimp_get_lists() {
	mailchimp_api_call( $data, "/lists", 'GET' );
}

function mailchimp_get_subscriber( $list_id, $email ) {

	$emailhash = md5( strtolower( $email) );
	$url = "/lists/" . $list_id . "/members/" . $emailhash;
	$response = mailchimp_api_call( $data, $url, 'GET' );

	return $response;
}

function mailchimp_update_subscriber( $list_id, $email, $subscriber ) {

	$emailhash = md5( strtolower( $email) );
	$url = "/lists/" . $list_id . "/members/" . $emailhash;
	$response = mailchimp_api_call( $subscriber, $url, 'PUT' );

	return $response;
}

function mailchimp_api_call( $data, $json_url, $request = 'GET' ) {

	$domain = "https://usx.api.mailchimp.com/3.0";
	$username = "username";
	$key = "key-usx";

	$json_body = json_encode($data, JSON_FORCE_OBJECT | JSON_PRETTY_PRINT);
	$header[] = "Content-type: application/json";
	$connection = curl_init("$domain/$json_url");
	curl_setopt($connection, CURLOPT_RETURNTRANSFER, true);
	curl_setopt($connection, CURLOPT_HTTPHEADER, $header);
	curl_setopt($connection, CURLOPT_HEADER, false);
	curl_setopt($connection, CURLOPT_USERPWD, $username . ':' . $key);
	curl_setopt($connection, CURLOPT_POST, true);
	curl_setopt($connection, CURLOPT_POSTFIELDS, $json_body);
	curl_setopt($connection, CURLOPT_CUSTOMREQUEST, $request);
	curl_setopt($connection, CURLOPT_VERBOSE, 1);
	$response = json_decode(curl_exec($connection), true);
	return $response;
}