convertkit / lib / class-convertkit-api.php

class-convertkit-api.php in Kit (formerly ConvertKit) – Email Newsletter, Email Marketing, Membership, Subscribers and Landing Pages 1.9.8.0, at lib/class-convertkit-api.php

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1	<?php
2	/**
3	* ConvertKit API class.
4	*
5	* @package ConvertKit
6	* @author ConvertKit
7	*/
8
9	/**
10	* ConvertKit API class
11	*
12	* @package ConvertKit
13	* @author ConvertKit
14	*/
15	class ConvertKit_API {
16
17	/**
18	* ConvertKit API Key
19	*
20	* @var bool\|string
21	*/
22	protected $api_key = false;
23
24	/**
25	* ConvertKit API Secret
26	*
27	* @var bool\|string
28	*/
29	protected $api_secret = false;
30
31	/**
32	* Save debug data to log
33	*
34	* @var bool
35	*/
36	protected $debug = false;
37
38	/**
39	* The plugin name.
40	*
41	* @var bool\|string
42	*/
43	protected $plugin_name;
44
45	/**
46	* The plugin path.
47	*
48	* @var bool\|string
49	*/
50	protected $plugin_path;
51
52	/**
53	* The plugin URL.
54	*
55	* @var bool\|string
56	*/
57	protected $plugin_url;
58
59	/**
60	* The plugin version.
61	*
62	* @var bool\|string
63	*/
64	protected $plugin_version;
65
66	/**
67	* Version of ConvertKit API
68	*
69	* @var string
70	*/
71	protected $api_version = 'v3';
72
73	/**
74	* ConvertKit API URL
75	*
76	* @var string
77	*/
78	protected $api_url_base = 'https://api.convertkit.com/';
79
80	/**
81	* Holds the log class for writing to the log file
82	*
83	* @var bool\|ConvertKit_Log
84	*/
85	public $log = false;
86
87	/**
88	* Holds an array of error messages, localized to the plugin
89	* using this API class.
90	*
91	* @var bool\|array
92	*/
93	public $error_messages = false;
94
95	/**
96	* Sets up the API with the required credentials.
97	*
98	* @since 1.9.6
99	*
100	* @param bool\|string $api_key ConvertKit API Key.
101	* @param bool\|string $api_secret ConvertKit API Secret.
102	* @param bool\|object $debug Save data to log.
103	*/
104	public function __construct( $api_key = false, $api_secret = false, $debug = false ) {
105
106	// Set API credentials, debugging and logging class.
107	$this->api_key = $api_key;
108	$this->api_secret = $api_secret;
109	$this->debug = $debug;
110	$this->plugin_name = ( defined( 'CONVERTKIT_PLUGIN_NAME' ) ? CONVERTKIT_PLUGIN_NAME : false );
111	$this->plugin_path = ( defined( 'CONVERTKIT_PLUGIN_PATH' ) ? CONVERTKIT_PLUGIN_PATH : false );
112	$this->plugin_url = ( defined( 'CONVERTKIT_PLUGIN_URL' ) ? CONVERTKIT_PLUGIN_URL : false );
113	$this->plugin_version = ( defined( 'CONVERTKIT_PLUGIN_VERSION' ) ? CONVERTKIT_PLUGIN_VERSION : false );
114
115	// Setup logging class if the required parameters exist.
116	if ( $this->debug && $this->plugin_path !== false ) {
117	$this->log = new ConvertKit_Log( $this->plugin_path );
118	}
119
120	// Define translatable / localized error strings.
121	// WordPress requires that the text domain be a string (e.g. 'woocommerce-convertkit') and not a variable,
122	// otherwise localization won't work.
123	// phpcs:disable
124	$this->error_messages = array(
125	// form_subscribe().
126	'form_subscribe_form_id_empty' => __( 'form_subscribe(): the form_id parameter is empty.', 'convertkit' ),
127	'form_subscribe_email_empty' => __( 'form_subscribe(): the email parameter is empty.', 'convertkit' ),
128
129	// sequence_subscribe().
130	'sequence_subscribe_sequence_id_empty' => __( 'sequence_subscribe(): the sequence_id parameter is empty.', 'convertkit' ),
131	'sequence_subscribe_email_empty' => __( 'sequence_subscribe(): the email parameter is empty.', 'convertkit' ),
132
133	// tag_subscribe().
134	'tag_subscribe_tag_id_empty' => __( 'tag_subscribe(): the tag_id parameter is empty.', 'convertkit' ),
135	'tag_subscribe_email_empty' => __( 'tag_subscribe(): the email parameter is empty.', 'convertkit' ),
136
137	// get_subscriber_by_email().
138	'get_subscriber_by_email_email_empty' => __( 'get_subscriber_by_email(): the email parameter is empty.', 'convertkit' ),
139	/* translators: Email Address */
140	'get_subscriber_by_email_none' => __( 'No subscriber(s) exist in ConvertKit matching the email address %s.', 'convertkit' ),
141
142	// get_subscriber_by_id().
143	'get_subscriber_by_id_subscriber_id_empty' => __( 'get_subscriber_by_id(): the subscriber_id parameter is empty.', 'convertkit' ),
144
145	// get_subscriber_tags().
146	'get_subscriber_tags_subscriber_id_empty' => __( 'get_subscriber_tags(): the subscriber_id parameter is empty.', 'convertkit' ),
147
148	// unsubscribe_email().
149	'unsubscribe_email_empty' => __( 'unsubscribe(): the email parameter is empty.', 'convertkit' ),
150
151	// get_all_posts().
152	'get_all_posts_posts_per_request_bound_too_low' => __( 'get_all_posts(): the posts_per_request parameter must be equal to or greater than 1.', 'convertkit' ),
153	'get_all_posts_posts_per_request_bound_too_high' => __( 'get_all_posts(): the posts_per_request parameter must be equal to or less than 50.', 'convertkit' ),
154
155	// get_posts().
156	'get_posts_page_parameter_bound_too_low' => __( 'get_posts(): the page parameter must be equal to or greater than 1.', 'convertkit' ),
157	'get_posts_per_page_parameter_bound_too_low' => __( 'get_posts(): the per_page parameter must be equal to or greater than 1.', 'convertkit' ),
158	'get_posts_per_page_parameter_bound_too_high' => __( 'get_posts(): the per_page parameter must be equal to or less than 50.', 'convertkit' ),
159
160	// request().
161	/* translators: HTTP method */
162	'request_method_unsupported' => __( 'API request method %s is not supported in ConvertKit_API class.', 'convertkit' ),
163	'request_rate_limit_exceeded' => __( 'Rate limit hit.', 'convertkit' ),
164	'response_type_unexpected' => __( 'The response from the API is not of the expected type array.', 'convertkit' ),
165	);
166	// phpcs:enable
167
168	}
169
170	/**
171	* Gets account information from the API.
172	*
173	* @since 1.9.6
174	*
175	* @return WP_Error\|array
176	*/
177	public function account() {
178
179	$this->log( 'API: account()' );
180
181	return $this->get(
182	'account',
183	array(
184	'api_secret' => $this->api_secret,
185	)
186	);
187
188	}
189
190	/**
191	* Gets all subscription forms from the API.
192	*
193	* @since 1.9.6
194	*
195	* @return WP_Error\|array
196	*/
197	public function get_subscription_forms() {
198
199	$this->log( 'API: get_subscription_forms()' );
200
201	// Send request.
202	return $this->get(
203	'subscription_forms',
204	array(
205	'api_key' => $this->api_key,
206	)
207	);
208
209	}
210
211	/**
212	* Gets all forms from the API.
213	*
214	* @since 1.9.6
215	*
216	* @return WP_Error\|array
217	*/
218	public function get_forms() {
219
220	$this->log( 'API: get_forms()' );
221
222	// Get all forms and landing pages from the API.
223	$forms = $this->get_forms_landing_pages();
224
225	// If an error occured, log and return it now.
226	if ( is_wp_error( $forms ) ) {
227	$this->log( 'API: get_forms(): Error: ' . $forms->get_error_message() );
228	return $forms;
229	}
230
231	return $forms['forms'];
232
233	}
234
235	/**
236	* Subscribes an email address to a form.
237	*
238	* @since 1.9.6
239	*
240	* @param int $form_id Form ID.
241	* @param string $email Email Address.
242	* @param string $first_name First Name.
243	* @param mixed $fields Custom Fields (false\|array).
244	* @param mixed $tag_ids Tags (false\|array).
245	* @return WP_Error\|array
246	*/
247	public function form_subscribe( $form_id, $email, $first_name = '', $fields = false, $tag_ids = false ) {
248
249	// Backward compat. if $email is an array comprising of email and name keys.
250	if ( is_array( $email ) ) { // @phpstan-ignore-line.
251	_deprecated_function( __FUNCTION__, '1.2.1', 'form_subscribe( $form_id, $email, $first_name )' );
252	$first_name = $email['name'];
253	$email = $email['email'];
254	}
255
256	$this->log( 'API: form_subscribe(): [ form_id: ' . $form_id . ', email: ' . $email . ', first_name: ' . $first_name . ' ]' );
257
258	// Sanitize some parameters.
259	$form_id = absint( $form_id );
260	$email = trim( $email );
261	$first_name = trim( $first_name );
262
263	// Return error if no Form ID or email address is specified.
264	if ( empty( $form_id ) ) {
265	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'form_subscribe_form_id_empty' ) );
266	}
267	if ( empty( $email ) ) {
268	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'form_subscribe_email_empty' ) );
269	}
270
271	// Build request parameters.
272	$params = array(
273	'api_key' => $this->api_key,
274	'email' => $email,
275	'first_name' => $first_name,
276	);
277	if ( $fields ) {
278	$params['fields'] = $fields;
279	}
280	if ( $tag_ids ) {
281	$params['tags'] = $tag_ids;
282	}
283
284	// Send request.
285	$response = $this->post( 'forms/' . $form_id . '/subscribe', $params );
286
287	// If an error occured, log and return it now.
288	if ( is_wp_error( $response ) ) {
289	$this->log( 'API: form_subscribe(): Error: ' . $response->get_error_message() );
290	return $response;
291	}
292
293	/**
294	* Runs actions immediately after the email address was successfully subscribed to the form.
295	*
296	* @since 1.2.1
297	*
298	* @param array $response API Response
299	* @param int $form_id Form ID
300	* @param string $email Email Address
301	* @param string $first_name First Name
302	* @param mixed $fields Custom Fields (false\|array)
303	* @param mixed $tag_ids Tags (false\|array)
304	*/
305	do_action( 'convertkit_api_form_subscribe_success', $response, $form_id, $email, $first_name, $fields, $tag_ids );
306
307	return $response;
308
309	}
310
311	/**
312	* Gets all landing pages from the API.
313	*
314	* @since 1.9.6
315	*
316	* @return WP_Error\|array
317	*/
318	public function get_landing_pages() {
319
320	$this->log( 'API: get_landing_pages()' );
321
322	// Get all forms and landing pages from the API.
323	$forms = $this->get_forms_landing_pages();
324
325	// If an error occured, log and return it now.
326	if ( is_wp_error( $forms ) ) {
327	$this->log( 'API: get_landing_pages(): Error: ' . $forms->get_error_message() );
328	return $forms;
329	}
330
331	return $forms['landing_pages'];
332
333	}
334
335	/**
336	* Fetches all sequences from the API.
337	*
338	* @since 1.9.6
339	*
340	* @return WP_Error\|array
341	*/
342	public function get_sequences() {
343
344	$this->log( 'API: get_sequences()' );
345
346	$sequences = array();
347
348	// Send request.
349	$response = $this->get(
350	'sequences',
351	array(
352	'api_key' => $this->api_key,
353	)
354	);
355
356	// If an error occured, log and return it now.
357	if ( is_wp_error( $response ) ) {
358	$this->log( 'API: get_sequences(): Error: ' . $response->get_error_message() );
359	return $response;
360	}
361
362	// If the response isn't an array as we expect, log that no sequences exist and return a blank array.
363	if ( ! is_array( $response['courses'] ) ) {
364	$this->log( 'API: get_sequences(): Error: No sequences exist in ConvertKit.' );
365	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'response_type_unexpected' ) );
366	}
367
368	// If no sequences exist, log that no sequences exist and return a blank array.
369	if ( ! count( $response['courses'] ) ) {
370	$this->log( 'API: get_sequences(): Error: No sequences exist in ConvertKit.' );
371	return $sequences;
372	}
373
374	foreach ( $response['courses'] as $sequence ) {
375	$sequences[] = $sequence;
376	}
377
378	return $sequences;
379
380	}
381
382	/**
383	* Subscribes an email address to a sequence.
384	*
385	* @since 1.9.6
386	*
387	* @param int $sequence_id Sequence ID.
388	* @param string $email Email Address.
389	* @param string $first_name First Name.
390	* @param mixed $fields Custom Fields (false\|array).
391	* @return WP_Error\|array
392	*/
393	public function sequence_subscribe( $sequence_id, $email, $first_name = '', $fields = false ) {
394
395	$this->log( 'API: sequence_subscribe(): [ sequence_id: ' . $sequence_id . ', email: ' . $email . ']' );
396
397	// Sanitize some parameters.
398	$sequence_id = absint( $sequence_id );
399	$email = trim( $email );
400	$first_name = trim( $first_name );
401
402	// Return error if no Sequence ID or email address is specified.
403	if ( empty( $sequence_id ) ) {
404	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'sequence_subscribe_sequence_id_empty' ) );
405	}
406	if ( empty( $email ) ) {
407	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'sequence_subscribe_email_empty' ) );
408	}
409
410	// Build request parameters.
411	$params = array(
412	'api_key' => $this->api_key,
413	'email' => $email,
414	'first_name' => $first_name,
415	);
416	if ( $fields ) {
417	$params['fields'] = $fields;
418	}
419
420	// Send request.
421	$response = $this->post( 'sequences/' . $sequence_id . '/subscribe', $params );
422
423	// If an error occured, log and return it now.
424	if ( is_wp_error( $response ) ) {
425	$this->log( 'API: sequence_subscribe(): Error: ' . $response->get_error_message() );
426	return $response;
427	}
428
429	/**
430	* Runs actions immediately after the email address was successfully subscribed to the sequence.
431	*
432	* @since 1.9.6
433	*
434	* @param array $response API Response
435	* @param int $sequence_id Sequence ID
436	* @param string $email Email Address
437	* @param mixed $fields Custom Fields (false\|array)
438	*/
439	do_action( 'convertkit_api_sequence_subscribe_success', $response, $sequence_id, $email, $fields );
440
441	return $response;
442
443	}
444
445	/**
446	* Fetches all tags from the API.
447	*
448	* @since 1.9.6
449	*
450	* @return WP_Error\|array
451	*/
452	public function get_tags() {
453
454	$this->log( 'API: get_tags()' );
455
456	$tags = array();
457
458	// Send request.
459	$response = $this->get(
460	'tags',
461	array(
462	'api_key' => $this->api_key,
463	)
464	);
465
466	// If an error occured, log and return it now.
467	if ( is_wp_error( $response ) ) {
468	$this->log( 'API: get_tags(): Error: ' . $response->get_error_message() );
469	return $response;
470	}
471
472	// If the response isn't an array as we expect, log that no tags exist and return a blank array.
473	if ( ! is_array( $response['tags'] ) ) {
474	$this->log( 'API: get_tags(): Error: No tags exist in ConvertKit.' );
475	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'response_type_unexpected' ) );
476	}
477
478	// If no tags exist, log that no tags exist and return a blank array.
479	if ( ! count( $response['tags'] ) ) {
480	$this->log( 'API: get_tags(): Error: No tags exist in ConvertKit.' );
481	return $tags;
482	}
483
484	foreach ( $response['tags'] as $tag ) {
485	$tags[] = $tag;
486	}
487
488	return $tags;
489
490	}
491
492	/**
493	* Subscribes an email address to a tag.
494	*
495	* @since 1.9.6
496	*
497	* @param int $tag_id Tag ID.
498	* @param string $email Email Address.
499	* @param string $first_name First Name.
500	* @param mixed $fields Custom Fields (false\|array).
501	* @return WP_Error\|array
502	*/
503	public function tag_subscribe( $tag_id, $email, $first_name = '', $fields = false ) {
504
505	$this->log( 'API: tag_subscribe(): [ tag_id: ' . $tag_id . ', email: ' . $email . ']' );
506
507	// Sanitize some parameters.
508	$tag_id = absint( $tag_id );
509	$email = trim( $email );
510	$first_name = trim( $first_name );
511
512	// Return error if no Tag ID or email address is specified.
513	if ( empty( $tag_id ) ) {
514	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'tag_subscribe_tag_id_empty' ) );
515	}
516	if ( empty( $email ) ) {
517	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'tag_subscribe_email_empty' ) );
518	}
519
520	// Build request parameters.
521	$params = array(
522	'api_key' => $this->api_key,
523	'email' => $email,
524	'first_name' => $first_name,
525	);
526	if ( $fields ) {
527	$params['fields'] = $fields;
528	}
529
530	// Send request.
531	$response = $this->post( 'tags/' . $tag_id . '/subscribe', $params );
532
533	// If an error occured, log and return it now.
534	if ( is_wp_error( $response ) ) {
535	$this->log( 'API: tag_subscribe(): Error: ' . $response->get_error_message() );
536	return $response;
537	}
538
539	/**
540	* Runs actions immediately after the email address was successfully subscribed to the tag.
541	*
542	* @since 1.9.6
543	*
544	* @param array $response API Response
545	* @param int $tag_id Tag ID
546	* @param string $email Email Address
547	* @param mixed $fields Custom Fields (false\|array).
548	*/
549	do_action( 'convertkit_api_tag_subscribe_success', $response, $tag_id, $email, $fields );
550
551	return $response;
552
553	}
554
555	/**
556	* Gets a subscriber by their email address.
557	*
558	* @since 1.9.6
559	*
560	* @param string $email Email Address.
561	* @return WP_Error\|array
562	*/
563	public function get_subscriber_by_email( $email ) {
564
565	$this->log( 'API: get_subscriber_by_email(): [ email: ' . $email . ']' );
566
567	// Sanitize some parameters.
568	$email = trim( $email );
569
570	// Return error if email address is specified.
571	if ( empty( $email ) ) {
572	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'get_subscriber_by_email_email_empty' ) );
573	}
574
575	// Send request.
576	$response = $this->get(
577	'subscribers',
578	array(
579	'api_secret' => $this->api_secret,
580	'email_address' => $email,
581	)
582	);
583
584	// If an error occured, log and return it now.
585	if ( is_wp_error( $response ) ) {
586	$this->log( 'API: get_subscriber_by_email(): Error: ' . $response->get_error_message() );
587	return $response;
588	}
589
590	// If no matching subscribers exist, log that no matching subscribers exist and return a blank array.
591	if ( (int) $response['total_subscribers'] === 0 ) {
592	$error = new WP_Error(
593	'convertkit_api_error',
594	sprintf(
595	$this->get_error_message( 'get_subscriber_by_email_none' ),
596	$email
597	)
598	);
599
600	$this->log( 'API: get_subscriber_by_email(): Error: ' . $error->get_error_message() );
601	return $error;
602	}
603
604	// Return subscriber.
605	return $response['subscribers'][0];
606
607	}
608
609	/**
610	* Gets a subscriber by their ConvertKit subscriber ID.
611	*
612	* @since 1.9.6
613	*
614	* @param int $subscriber_id Subscriber ID.
615	* @return WP_Error\|array
616	*/
617	public function get_subscriber_by_id( $subscriber_id ) {
618
619	$this->log( 'API: get_subscriber_by_id(): [ subscriber_id: ' . $subscriber_id . ']' );
620
621	// Sanitize some parameters.
622	$subscriber_id = absint( $subscriber_id );
623
624	// Return error if no Subscriber ID is specified.
625	if ( empty( $subscriber_id ) ) {
626	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'get_subscriber_by_id_subscriber_id_empty' ) );
627	}
628
629	// Send request.
630	$response = $this->get(
631	'subscribers/' . $subscriber_id,
632	array(
633	'api_secret' => $this->api_secret,
634	)
635	);
636
637	// If an error occured, log and return it now.
638	if ( is_wp_error( $response ) ) {
639	$this->log( 'API: get_subscriber_by_id(): Error: ' . $response->get_error_message() );
640	return $response;
641	}
642
643	return $response['subscriber'];
644
645	}
646
647	/**
648	* Gets a list of tags for the given ConvertKit subscriber ID.
649	*
650	* @since 1.9.6
651	*
652	* @param int $subscriber_id Subscriber ID.
653	* @return WP_Error\|array
654	*/
655	public function get_subscriber_tags( $subscriber_id ) {
656
657	$this->log( 'API: get_subscriber_tags(): [ subscriber_id: ' . $subscriber_id . ']' );
658
659	// Sanitize some parameters.
660	$subscriber_id = absint( $subscriber_id );
661
662	// Return error if no Subscriber ID is specified.
663	if ( empty( $subscriber_id ) ) {
664	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'get_subscriber_tags_subscriber_id_empty' ) );
665	}
666
667	// Send request.
668	$response = $this->get(
669	'subscribers/' . $subscriber_id . '/tags',
670	array(
671	'api_key' => $this->api_key,
672	)
673	);
674
675	// If an error occured, log and return it now.
676	if ( is_wp_error( $response ) ) {
677	$this->log( 'API: get_subscriber_tags(): Error: ' . $response->get_error_message() );
678	return $response;
679	}
680
681	return $response['tags'];
682
683	}
684
685	/**
686	* Returns the subscriber's ID by their email address.
687	*
688	* @since 1.9.6
689	*
690	* @param string $email_address Email Address.
691	* @return WP_Error\|int
692	*/
693	public function get_subscriber_id( $email_address ) {
694
695	// Get subscriber.
696	$subscriber = $this->get_subscriber_by_email( $email_address );
697
698	// If an error occured, log and return it now.
699	if ( is_wp_error( $subscriber ) ) {
700	return $subscriber;
701	}
702
703	// Return ID.
704	return $subscriber['id'];
705
706	}
707
708	/**
709	* Unsubscribes an email address.
710	*
711	* @since 1.9.6
712	*
713	* @param string $email Email Address.
714	* @return WP_Error\|array
715	*/
716	public function unsubscribe( $email ) {
717
718	$this->log( 'API: unsubscribe(): [ email: ' . $email . ']' );
719
720	// Sanitize some parameters.
721	$email = trim( $email );
722
723	// Return error if no email address is specified.
724	if ( empty( $email ) ) {
725	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'unsubscribe_email_empty' ) );
726	}
727
728	// Send request.
729	$response = $this->put(
730	'unsubscribe',
731	array(
732	'api_secret' => $this->api_secret,
733	'email' => $email,
734	)
735	);
736
737	// If an error occured, log and return it now.
738	if ( is_wp_error( $response ) ) {
739	$this->log( 'API: unsubscribe(): Error: ' . $response->get_error_message() );
740	return $response;
741	}
742
743	/**
744	* Runs actions immediately after the email address was successfully unsubscribed.
745	*
746	* @since 1.9.6
747	*
748	* @param array $response API Response
749	* @param string $email Email Address
750	*/
751	do_action( 'convertkit_api_form_unsubscribe_success', $response, $email );
752
753	return $response;
754
755	}
756
757	/**
758	* Gets all custom fields from the API.
759	*
760	* @since 1.9.6.9
761	*
762	* @return WP_Error\|array
763	*/
764	public function get_custom_fields() {
765
766	$this->log( 'API: get_custom_fields()' );
767
768	$custom_fields = array();
769
770	// Send request.
771	$response = $this->get(
772	'custom_fields',
773	array(
774	'api_key' => $this->api_key,
775	)
776	);
777
778	// If an error occured, return WP_Error.
779	if ( is_wp_error( $response ) ) {
780	$this->log( 'API: get_custom_fields(): Error: ' . $response->get_error_message() );
781	return $response;
782	}
783
784	// If the response isn't an array as we expect, log that no tags exist and return a blank array.
785	if ( ! is_array( $response['custom_fields'] ) ) {
786	$this->log( 'API: get_custom_fields(): Error: No custom fields exist in ConvertKit.' );
787	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'response_type_unexpected' ) );
788	}
789
790	// If no custom fields exist, log that no custom fields exist and return a blank array.
791	if ( ! count( $response['custom_fields'] ) ) {
792	$this->log( 'API: get_custom_fields(): Error: No custom fields exist in ConvertKit.' );
793	return $custom_fields;
794	}
795
796	foreach ( $response['custom_fields'] as $custom_field ) {
797	$custom_fields[] = $custom_field;
798	}
799
800	return $custom_fields;
801
802	}
803
804	/**
805	* Gets all posts from the API.
806	*
807	* @since 1.9.7.6
808	*
809	* @param int $posts_per_request Number of Posts to fetch in each request.
810	* @return WP_Error\|array
811	*/
812	public function get_all_posts( $posts_per_request = 50 ) {
813
814	$this->log( 'API: get_all_posts()' );
815
816	// Sanitize some parameters.
817	$posts_per_request = absint( $posts_per_request );
818
819	// Sanity check that parameters aren't outside of the bounds as defined by the API.
820	if ( $posts_per_request < 1 ) {
821	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'get_all_posts_posts_per_request_bound_too_low' ) );
822	}
823	if ( $posts_per_request > 50 ) {
824	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'get_all_posts_posts_per_request_bound_too_high' ) );
825	}
826
827	// Define an array to store the posts in.
828	$posts = array();
829
830	// Mock the response to start the while loop.
831	$response = array(
832	'page' => 0, // Start on page zero, as the below loop will add 1 to this.
833	'total_pages' => 1, // We always know there will be one page of posts.
834	);
835
836	// Iterate through each page of posts.
837	while ( absint( $response['total_pages'] ) >= absint( $response['page'] ) + 1 ) {
838	// Fetch posts.
839	$response = $this->get_posts( absint( $response['page'] ) + 1, $posts_per_request );
840
841	// Bail if an error occured.
842	if ( is_wp_error( $response ) ) {
843	return $response;
844	}
845
846	// Exit loop if no posts exist.
847	if ( ! count( $response ) ) {
848	break;
849	}
850
851	// Append posts to array.
852	foreach ( $response['posts'] as $post ) {
853	$posts[] = $post;
854	}
855	}
856
857	// If no posts exist, log an error.
858	if ( ! count( $posts ) ) {
859	$this->log( 'API: get_posts(): Error: No broadcasts exist in ConvertKit.' );
860	}
861
862	// Return posts.
863	return $posts;
864
865	}
866
867	/**
868	* Gets posts from the API.
869	*
870	* @since 1.9.7.4
871	*
872	* @param int $page Page number.
873	* @param int $per_page Number of Posts to return.
874	* @return WP_Error\|array
875	*/
876	public function get_posts( $page = 1, $per_page = 10 ) {
877
878	$this->log( 'API: get_posts()' );
879
880	// Sanitize some parameters.
881	$page = absint( $page );
882	$per_page = absint( $per_page );
883
884	// Sanity check that parameters aren't outside of the bounds as defined by the API.
885	if ( $page < 1 ) {
886	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'get_posts_page_parameter_bound_too_low' ) );
887	}
888	if ( $per_page < 1 ) {
889	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'get_posts_per_page_parameter_bound_too_low' ) );
890	}
891	if ( $per_page > 50 ) {
892	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'get_posts_per_page_parameter_bound_too_high' ) );
893	}
894
895	$posts = array();
896
897	// Send request.
898	$response = $this->get(
899	'posts',
900	array(
901	'api_key' => $this->api_key,
902	'api_secret' => $this->api_secret,
903	'page' => $page,
904	'per_page' => $per_page,
905	)
906	);
907
908	// If an error occured, return WP_Error.
909	if ( is_wp_error( $response ) ) {
910	$this->log( 'API: get_posts(): Error: ' . $response->get_error_message() );
911	return $response;
912	}
913
914	// If the response isn't an array as we expect, log that no posts exist and return a blank array.
915	if ( ! is_array( $response['posts'] ) ) {
916	$this->log( 'API: get_posts(): Error: No broadcasts exist in ConvertKit.' );
917	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'response_type_unexpected' ) );
918	}
919
920	// If no posts exist, log that no posts exist and return a blank array.
921	if ( ! count( $response['posts'] ) ) {
922	$this->log( 'API: get_posts(): Error: No broadcasts exist in ConvertKit.' );
923	return $posts;
924	}
925
926	return $response;
927
928	}
929
930	/**
931	* Get HTML from ConvertKit for the given Legacy Form ID.
932	*
933	* This isn't specifically an API function, but for now it's best suited here.
934	*
935	* @param int $id Form ID.
936	* @return WP_Error\|string HTML
937	*/
938	public function get_form_html( $id ) {
939
940	// Define Legacy Form URL.
941	$url = add_query_arg(
942	array(
943	'k' => $this->api_key,
944	'v' => 2,
945	),
946	'https://api.convertkit.com/forms/' . $id . '/embed'
947	);
948
949	// Get HTML.
950	$body = $this->get_html( $url );
951
952	return $body;
953
954	}
955
956	/**
957	* Get HTML from ConvertKit for the given Landing Page URL.
958	*
959	* This isn't specifically an API function, but for now it's best suited here.
960	*
961	* @param string $url URL of Landing Page.
962	* @return string HTML
963	*/
964	public function get_landing_page_html( $url ) {
965
966	// Get HTML.
967	$body = $this->get_html( $url, false );
968
969	// Inject JS for subscriber forms to work.
970	$scripts = new WP_Scripts();
971	$script = "<script type='text/javascript' src='" . trailingslashit( $scripts->base_url ) . "wp-includes/js/jquery/jquery.js?ver=1.4.0'></script>"; // phpcs:ignore
972	$script .= "<script type='text/javascript' src='" . $this->plugin_url . 'resources/frontend/js/convertkit.js?ver=' . $this->plugin_version . "'></script>"; // phpcs:ignore
973	$script .= "<script type='text/javascript'>/* <![CDATA[ /var convertkit = {\"ajaxurl\":\"" . admin_url( 'admin-ajax.php' ) . '"};/ ]]> */</script>'; // phpcs:ignore
974
975	$body = str_replace( '</head>', '</head>' . $script, $body );
976
977	return $body;
978
979	}
980
981	/**
982	* Create a Purchase.
983	*
984	* @since 1.9.6.9
985	*
986	* @param array $purchase Purchase Data.
987	* @return WP_Error\|array
988	*/
989	public function purchase_create( $purchase ) {
990
991	$this->log( 'API: purchase_create(): [ purchase: ' . print_r( $purchase, true ) . ']' ); // phpcs:ignore
992
993	$response = $this->post(
994	'purchases',
995	array(
996	'api_secret' => $this->api_secret,
997	'purchase' => $purchase,
998	)
999	);
1000
1001	if ( is_wp_error( $response ) ) {
1002	$this->log( 'API: purchase_create(): Error: ' . $response->get_error_message() );
1003	}
1004
1005	/**
1006	* Runs actions immediately after the purchase data address was successfully created.
1007	*
1008	* @since 1.9.6.9
1009	*
1010	* @param array $response API Response
1011	* @param array $purchase Purchase Data
1012	*/
1013	do_action( 'convertkit_api_purchase_create_success', $response, $purchase );
1014
1015	return $response;
1016
1017	}
1018
1019	/**
1020	* Backward compat. function for updating Forms, Landing Pages and Tags in WordPress options table.
1021	*
1022	* @since 1.0.0
1023	*
1024	* @param string $api_key API Key.
1025	* @param string $api_secret API Secret.
1026	*/
1027	public function update_resources( $api_key, $api_secret ) { // phpcs:ignore
1028
1029	// Warn the developer that they shouldn't use this function.
1030	_deprecated_function( __FUNCTION__, '1.9.6', 'refresh() in ConvertKit_Resource_Forms, ConvertKit_Resource_Landing_Pages and ConvertKit_Resource_Tags classes.' );
1031
1032	// Initialize resource classes.
1033	$forms = new ConvertKit_Resource_Forms();
1034	$landing_pages = new ConvertKit_Resource_Landing_Pages();
1035	$tags = new ConvertKit_Resource_Tags();
1036
1037	// Refresh resources by calling the API and storing the results.
1038	$forms->refresh();
1039	$landing_pages->refresh();
1040	$tags->refresh();
1041
1042	}
1043
1044	/**
1045	* Backward compat. function for getting a ConvertKit subscriber by their ID.
1046	*
1047	* @since 1.9.6
1048	*
1049	* @param int $id Subscriber ID.
1050	* @return WP_Error\|array
1051	*/
1052	public function get_subscriber( $id ) {
1053
1054	// Warn the developer that they shouldn't use this function.
1055	_deprecated_function( __FUNCTION__, '1.9.6', 'get_subscriber_by_id()' );
1056
1057	// Pass request to new function.
1058	return $this->get_subscriber_by_id( $id );
1059
1060	}
1061
1062	/**
1063	* Backward compat. function for subscribing a ConvertKit subscriber to the given Tag.
1064	*
1065	* @since 1.9.6
1066	*
1067	* @param int $tag Tag ID.
1068	* @param array $args Arguments.
1069	* @return WP_Error\|array
1070	*/
1071	public function add_tag( $tag, $args ) {
1072
1073	// Warn the developer that they shouldn't use this function.
1074	_deprecated_function( __FUNCTION__, '1.9.6', 'tag_subscribe( $tag_id, $email_address )' );
1075
1076	// Pass request to new function.
1077	return $this->tag_subscribe( $tag, $args['email'] );
1078
1079	}
1080
1081	/**
1082	* Backward compat. function for fetching Legacy Form or Landing Page markup for the given URL.
1083	*
1084	* @since 1.9.6
1085	*
1086	* @param string $url URL.
1087	* @return WP_Error\|string
1088	*/
1089	public function get_resource( $url ) {
1090
1091	// Warn the developer that they shouldn't use this function.
1092	_deprecated_function( __FUNCTION__, '1.9.6', 'get_form_html( $form_id ) or get_landing_page_html( $url )' );
1093
1094	// Pass request to new function.
1095	return $this->get_landing_page_html( $url );
1096
1097	}
1098
1099	/**
1100	* Backward compat. function for fetching Legacy Form or Landing Page markup for the given URL.
1101	*
1102	* @since 1.9.6
1103	*
1104	* @param array $args Arguments (single email key).
1105	* @return WP_Error\|array
1106	*/
1107	public function form_unsubscribe( $args ) {
1108
1109	// Warn the developer that they shouldn't use this function.
1110	_deprecated_function( __FUNCTION__, '1.9.6', 'unsubscribe( $email_address )' );
1111
1112	// Pass request to new function.
1113	return $this->unsubscribe( $args['email'] );
1114
1115	}
1116
1117	/**
1118	* Adds the given entry to the log file, if debugging is enabled.
1119	*
1120	* @since 1.9.6
1121	*
1122	* @param string $entry Log Entry.
1123	*/
1124	public function log( $entry ) {
1125
1126	// Don't log this entry if debugging is disabled.
1127	if ( ! $this->debug ) {
1128	return;
1129	}
1130
1131	// Don't log this entry if the logging class was not initialized.
1132	if ( ! $this->log ) {
1133	return;
1134	}
1135
1136	// Pass the request to the ConvertKit_Log class.
1137	$this->log->add( $entry );
1138
1139	}
1140
1141	/**
1142	* Get HTML for the given URL.
1143	*
1144	* This isn't specifically an API function, but for now it's best suited here.
1145	*
1146	* @param string $url URL of Form or Landing Page.
1147	* @param bool $body_only Return HTML between <body> and </body> tags only.
1148	* @return WP_Error\|string
1149	*/
1150	private function get_html( $url, $body_only = true ) {
1151
1152	// Get HTML from URL.
1153	$result = wp_remote_get(
1154	$url,
1155	array(
1156	'Accept-Encoding' => 'gzip',
1157	'timeout' => $this->get_timeout(),
1158	'user-agent' => $this->get_user_agent(),
1159	)
1160	);
1161
1162	// If an error occured, log and return it now.
1163	if ( is_wp_error( $result ) ) {
1164	return $result;
1165	}
1166
1167	// Fetch HTTP response code and body.
1168	$http_response_code = wp_remote_retrieve_response_code( $result );
1169	$body = wp_remote_retrieve_body( $result );
1170
1171	// If the body appears to be JSON containing an error, the request for a Legacy Form
1172	// through api.convertkit.com failed, so return a WP_Error now.
1173	if ( $this->is_json( $body ) ) {
1174	$json = json_decode( $body );
1175	return new WP_Error(
1176	'convertkit_api_error',
1177	sprintf(
1178	'ConvertKit: %s',
1179	$json->error_message
1180	)
1181	);
1182	}
1183
1184	// Get just the scheme and host from the URL.
1185	$url_scheme = wp_parse_url( $url );
1186	$url_scheme_host_only = $url_scheme['scheme'] . '://' . $url_scheme['host'];
1187
1188	// Load the landing page HTML into a DOMDocument.
1189	libxml_use_internal_errors( true );
1190	$html = new DOMDocument();
1191	if ( $body_only ) {
1192	// Prevent DOMDocument from including a doctype on saveHTML().
1193	// We don't use LIBXML_HTML_NOIMPLIED, as it requires a single root element, which Legacy Forms don't have.
1194	$html->loadHTML( mb_convert_encoding( $body, 'HTML-ENTITIES', 'UTF-8' ), LIBXML_HTML_NODEFDTD );
1195	} else {
1196	$html->loadHTML( mb_convert_encoding( $body, 'HTML-ENTITIES', 'UTF-8' ) );
1197	}
1198
1199	// Convert any relative URLs to absolute URLs in the HTML DOM.
1200	$this->convert_relative_to_absolute_urls( $html->getElementsByTagName( 'a' ), 'href', $url_scheme_host_only );
1201	$this->convert_relative_to_absolute_urls( $html->getElementsByTagName( 'link' ), 'href', $url_scheme_host_only );
1202	$this->convert_relative_to_absolute_urls( $html->getElementsByTagName( 'img' ), 'src', $url_scheme_host_only );
1203	$this->convert_relative_to_absolute_urls( $html->getElementsByTagName( 'script' ), 'src', $url_scheme_host_only );
1204	$this->convert_relative_to_absolute_urls( $html->getElementsByTagName( 'form' ), 'action', $url_scheme_host_only );
1205
1206	// If the entire HTML needs to be returned, return it now.
1207	if ( ! $body_only ) {
1208	return $html->saveHTML();
1209	}
1210
1211	// Remove some HTML tags that DOMDocument adds, returning the output.
1212	// We do this instead of using LIBXML_HTML_NOIMPLIED in loadHTML(), because Legacy Forms are not always contained in
1213	// a single root / outer element, which is required for LIBXML_HTML_NOIMPLIED to correctly work.
1214	return $this->strip_html_head_body_tags( $html->saveHTML() );
1215
1216	}
1217
1218	/**
1219	* Determines if the given string is JSON.
1220	*
1221	* @since 1.9.6.4
1222	*
1223	* @param string $string Possible JSON String.
1224	* @return bool Is JSON String.
1225	*/
1226	private function is_json( $string ) {
1227
1228	json_decode( $string );
1229	return json_last_error() === JSON_ERROR_NONE;
1230
1231	}
1232
1233	/**
1234	* Converts any relative URls to absolute, fully qualified HTTP(s) URLs for the given
1235	* DOM Elements.
1236	*
1237	* @since 1.9.6
1238	*
1239	* @param DOMNodeList<DOMElement> $elements Elements.
1240	* @param string $attribute HTML Attribute.
1241	* @param string $url Absolute URL to prepend to relative URLs.
1242	*/
1243	private function convert_relative_to_absolute_urls( $elements, $attribute, $url ) {
1244
1245	// Anchor hrefs.
1246	foreach ( $elements as $element ) {
1247	// Skip if the attribute's value is empty.
1248	if ( empty( $element->getAttribute( $attribute ) ) ) {
1249	continue;
1250	}
1251
1252	// Skip if the attribute's value is a fully qualified URL.
1253	if ( filter_var( $element->getAttribute( $attribute ), FILTER_VALIDATE_URL ) ) {
1254	continue;
1255	}
1256
1257	// Skip if this is a Google Font CSS URL.
1258	if ( strpos( $element->getAttribute( $attribute ), '//fonts.googleapis.com' ) !== false ) {
1259	continue;
1260	}
1261
1262	// If here, the attribute's value is a relative URL, missing the http(s) and domain.
1263	// Prepend the URL to the attribute's value.
1264	$element->setAttribute( $attribute, $url . $element->getAttribute( $attribute ) );
1265	}
1266
1267	}
1268
1269	/**
1270	* Strips <html>, <head> and <body> opening and closing tags from the given markup.
1271	*
1272	* @since 1.9.6.5
1273	*
1274	* @param string $markup HTML Markup.
1275	* @return string HTML Markup
1276	* */
1277	private function strip_html_head_body_tags( $markup ) {
1278
1279	$markup = str_replace( '<html>', '', $markup );
1280	$markup = str_replace( '</html>', '', $markup );
1281	$markup = str_replace( '<head>', '', $markup );
1282	$markup = str_replace( '</head>', '', $markup );
1283	$markup = str_replace( '<body>', '', $markup );
1284	$markup = str_replace( '</body>', '', $markup );
1285
1286	return $markup;
1287
1288	}
1289
1290	/**
1291	* Gets all forms and landing pages from the API.
1292	*
1293	* @since 1.9.6
1294	*
1295	* @return WP_Error\|array
1296	*/
1297	private function get_forms_landing_pages() {
1298
1299	// Send request.
1300	$response = $this->get(
1301	'forms',
1302	array(
1303	'api_key' => $this->api_key,
1304	)
1305	);
1306
1307	// If an error occured, log and return it now.
1308	if ( is_wp_error( $response ) ) {
1309	return $response;
1310	}
1311
1312	// Iterate through forms, determining if each form is a form or landing page.
1313	$forms = array();
1314	$landing_pages = array();
1315	foreach ( $response['forms'] as $form ) {
1316	// Skip archived forms.
1317	if ( isset( $form['archived'] ) && $form['archived'] ) {
1318	continue;
1319	}
1320
1321	switch ( $form['type'] ) {
1322	case 'hosted':
1323	$landing_pages[ $form['id'] ] = $form;
1324	break;
1325
1326	default:
1327	$forms[ $form['id'] ] = $form;
1328	break;
1329	}
1330	}
1331
1332	return array(
1333	'forms' => $forms,
1334	'landing_pages' => $landing_pages,
1335	);
1336
1337	}
1338
1339	/**
1340	* Performs a GET request.
1341	*
1342	* @since 1.9.6
1343	*
1344	* @param string $endpoint API Endpoint.
1345	* @param array $params Params.
1346	* @return WP_Error\|array
1347	*/
1348	private function get( $endpoint, $params ) {
1349
1350	return $this->request( $endpoint, 'get', $params, true );
1351
1352	}
1353
1354	/**
1355	* Performs a POST request.
1356	*
1357	* @since 1.9.6
1358	*
1359	* @param string $endpoint API Endpoint.
1360	* @param array $params Params.
1361	* @return WP_Error\|array
1362	*/
1363	private function post( $endpoint, $params ) {
1364
1365	return $this->request( $endpoint, 'post', $params, true );
1366
1367	}
1368
1369	/**
1370	* Performs a PUT request.
1371	*
1372	* @since 1.9.7.8
1373	*
1374	* @param string $endpoint API Endpoint.
1375	* @param array $params Params.
1376	* @return WP_Error\|array
1377	*/
1378	private function put( $endpoint, $params ) {
1379
1380	return $this->request( $endpoint, 'put', $params, true );
1381
1382	}
1383
1384	/**
1385	* Main function which handles sending requests to the API using WordPress functions.
1386	*
1387	* @since 1.9.6
1388	*
1389	* @param string $endpoint API Endpoint (required).
1390	* @param string $method HTTP Method (optional).
1391	* @param mixed $params Params (array\|boolean\|string).
1392	* @param bool $retry_if_rate_limit_hit Retry request if rate limit hit.
1393	* @return WP_Error\|array
1394	*/
1395	private function request( $endpoint, $method = 'get', $params = array(), $retry_if_rate_limit_hit = true ) {
1396
1397	// Send request.
1398	switch ( $method ) {
1399	case 'get':
1400	$result = wp_remote_get(
1401	$this->add_params_to_url( $this->get_api_url( $endpoint ), $params ),
1402	array(
1403	'Accept-Encoding' => 'gzip',
1404	'timeout' => $this->get_timeout(),
1405	'user-agent' => $this->get_user_agent(),
1406	)
1407	);
1408	break;
1409
1410	case 'post':
1411	$result = wp_remote_post(
1412	$this->get_api_url( $endpoint ),
1413	array(
1414	'Accept-Encoding' => 'gzip',
1415	'headers' => array(
1416	'Content-Type' => 'application/json; charset=utf-8',
1417	),
1418	'body' => wp_json_encode( $params ),
1419	'timeout' => $this->get_timeout(),
1420	'user-agent' => $this->get_user_agent(),
1421	)
1422	);
1423	break;
1424
1425	case 'put':
1426	$result = wp_remote_request(
1427	$this->get_api_url( $endpoint ),
1428	array(
1429	'method' => 'PUT',
1430	'Accept-Encoding' => 'gzip',
1431	'headers' => array(
1432	'Content-Type' => 'application/json; charset=utf-8',
1433	),
1434	'body' => wp_json_encode( $params ),
1435	'timeout' => $this->get_timeout(),
1436	'user-agent' => $this->get_user_agent(),
1437	)
1438	);
1439	break;
1440
1441	default:
1442	$result = new WP_Error(
1443	'convertkit_api_error',
1444	sprintf(
1445	$this->get_error_message( 'request_method_unsupported' ),
1446	$method
1447	)
1448	);
1449	break;
1450	}
1451
1452	// If an error occured, log and return it now.
1453	if ( is_wp_error( $result ) ) {
1454	$this->log( 'API: Error: ' . $result->get_error_message() );
1455	return $result;
1456	}
1457
1458	// Fetch HTTP response code and body.
1459	$http_response_code = wp_remote_retrieve_response_code( $result );
1460	$body = wp_remote_retrieve_body( $result );
1461	$response = json_decode( $body, true );
1462
1463	// If the HTTP response code is 429, we've hit the API's rate limit of 120 requests over 60 seconds.
1464	if ( $http_response_code === 429 ) {
1465	// If retry on rate limit hit is disabled, return a WP_Error.
1466	if ( ! $retry_if_rate_limit_hit ) {
1467	return new WP_Error( 'convertkit_api_error', $this->get_error_message( 'request_rate_limit_exceeded' ) );
1468	}
1469
1470	// Retry the request a final time, waiting 2 seconds before.
1471	sleep( 2 );
1472	return $this->request( $endpoint, $method, $params, false );
1473	}
1474
1475	// If an error message or code exists in the response, return a WP_Error.
1476	if ( isset( $response['error'] ) ) {
1477	$this->log( 'API: Error: ' . $response['error'] . ': ' . $response['message'] );
1478	return new WP_Error( 'convertkit_api_error', $response['error'] . ': ' . $response['message'] );
1479	}
1480
1481	return $response;
1482
1483	}
1484
1485	/**
1486	* Returns the maximum amount of time to wait for
1487	* a response to the request before exiting.
1488	*
1489	* @since 1.9.6
1490	*
1491	* @return int Timeout, in seconds.
1492	*/
1493	private function get_timeout() {
1494
1495	$timeout = 10;
1496
1497	/**
1498	* Defines the maximum time to allow the API request to run.
1499	*
1500	* @since 2.2.9
1501	*
1502	* @param int $timeout Timeout, in seconds.
1503	*/
1504	$timeout = apply_filters( 'convertkit_api_get_timeout', $timeout );
1505
1506	return $timeout;
1507
1508	}
1509
1510	/**
1511	* Gets a customized version of the WordPress default user agent; includes WP Version, PHP version, and ConvertKit plugin version.
1512	*
1513	* @since 1.9.6
1514	*
1515	* @return string User Agent
1516	*/
1517	private function get_user_agent() {
1518
1519	global $wp_version;
1520
1521	// Include an unmodified $wp_version.
1522	require ABSPATH . WPINC . '/version.php';
1523
1524	return sprintf(
1525	'WordPress/%1$s;PHP/%2$s;%3$s/%4$s;%5$s',
1526	$wp_version,
1527	phpversion(),
1528	$this->plugin_name,
1529	$this->plugin_version,
1530	home_url( '/' )
1531	);
1532
1533	}
1534
1535	/**
1536	* Returns the full API URL for the given endpoint.
1537	*
1538	* @since 1.9.6
1539	*
1540	* @param string $endpoint Endpoint.
1541	* @return string API URL
1542	*/
1543	private function get_api_url( $endpoint ) {
1544
1545	// For the /posts endpoint, the API base is https://api.convertkit.com/api/v3/$endpoint.
1546	if ( $endpoint === 'posts' ) {
1547	return path_join( $this->api_url_base . 'api/' . $this->api_version, $endpoint );
1548	}
1549
1550	// For all other endpoints, it's https://api.convertkit.com/v3/$endpoint.
1551	return path_join( $this->api_url_base . $this->api_version, $endpoint );
1552
1553	}
1554
1555	/**
1556	* Adds the supplied array of parameters as query arguments to the URL.
1557	*
1558	* @since 1.9.6.9
1559	*
1560	* @param string $url URL.
1561	* @param array $params Parameters for request.
1562	* @return string URL with API Key or API Secret
1563	*/
1564	private function add_params_to_url( $url, $params ) {
1565
1566	return add_query_arg( $params, $url );
1567
1568	}
1569
1570	/**
1571	* Returns the localized/translated error message for the given error key.
1572	*
1573	* @since 1.9.7.8
1574	*
1575	* @param string $key Key.
1576	* @return string Error message
1577	*/
1578	private function get_error_message( $key ) {
1579
1580	// Return a blank string if no error messages have been defined.
1581	if ( ! is_array( $this->error_messages ) ) {
1582	return '';
1583	}
1584
1585	// Return a blank string if the error message isn't defined.
1586	if ( ! array_key_exists( $key, $this->error_messages ) ) {
1587	return '';
1588	}
1589
1590	// Return error message.
1591	return $this->error_messages[ $key ];
1592
1593	}
1594
1595	}
1596