JSON API

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JSON API allows you to retrieve and manipulate WordPress content using HTTP requests. There are three main goals: Provide a simple, consistent external interface Create a stable, understandable internal implementation Enable new types of extensions for WordPress This plugin was created at The Museum of Modern Art for the weblog Inside/Out, which is served from Ruby on Rails. Instead of reimplementing the site templates as a WordPress theme, we opted for a Rails front-end that displays content served from a WordPress back-end. JSON API provides the necessary interface for retrieving content and accepting comment submissions. See the Other Notes section for the complete documentation. Documentation General concepts 1.1. Requests 1.2. Controllers 1.3. Responses Request methods 2.1. Core controller methods 2.2. Posts controller methods 2.3. Respond controller methods 2.4. Widgets controller methods Request arguments 3.1. Output-modifying arguments 3.2. Content-modifying arguments 3.3. Using include/exclude and redirects Response objects 4.1. Post response object 4.2. Category response object 4.3. Tag response object 4.4. Author response object 4.5. Comment response object 4.6. Attachment response object Extending JSON API 5.1. Plugin hooks 5.2. Developing JSON API controllers 5.3. Configuration options Unit tests 6.1. Preparing a WordPress test site 6.2. Running the tests 1. General Concepts 1.1. Requests Requests use a simple REST-style HTTP GET or POST. To invoke the API, include a non-empty query value for json in the URL. JSON API operates in two modes: Implicit mode is triggered by setting the json query var to a non-empty value on any WordPress page. The content that would normally appear on that page is returned in JSON format. Explicit mode is triggered by setting json to a known method string. See Section 2: Request methods for a complete method listing. Implicit mode examples: http://www.example.org/?json=1 http://www.example.org/?p=47&json=1 http://www.example.org/tag/banana/?json=1 Explicit mode examples: http://www.example.org/?json=get_recent_posts http://www.example.org/?json=get_post&post_id=47 http://www.example.org/?json=get_tag_posts&tag_slug=banana With user-friendly permalinks configured: http://www.example.org/api/get_recent_posts/ http://www.example.org/api/get_post/?post_id=47 http://www.example.org/api/get_tag_posts/?tag_slug=banana Further reading See Section 3: Request arguments for more information about request arguments to modify the response. 1.2. Controllers The 1.0 release of JSON API introduced a modular controller system. This allows developers to flexibly add features to the API and give users more control over which methods they have enabled. The Core controller Most of the methods available prior to version 1.0 have been moved to the Core controller. The two exceptions are submit_comment and create_post which are now available from the Respond and Posts controllers, respectively. The Core controller is the only one enabled by default. All other functionality must be enabled from the JSON API Settings page (under Settings in the WordPress admin menu). Specifying a controller There are a few ways of specifying a controller, depending on how you are calling the API: http://www.example.org/?json=get_recent_posts (core controller is implied, method is get_recent_posts) http://www.example.org/api/info/ (core controller is implied) http://www.example.org/api/core/get_category_posts/ (core controller can also be explicitly specified) http://www.example.org/?json=respond.submit_comment (respond controller, submit_comment method) Legacy compatibility JSON API retains support for its pre-1.0 methods. For example, if you invoke the method create_post without a controller specified, the Posts controller is chosen instead of Core. Available controllers The current release includes three controllers: Core, Posts, and Respond. Developers are encouraged to suggest or submit additional controllers. Further reading See Section 2: Request methods for a complete reference of available controllers and methods. For documentation on extending JSON API with new controllers see Section 5.2: Developing JSON API controllers. 1.3. Responses The standard response format for JSON API is (as you may have guessed) JSON. Here is an example response from http://localhost/wordpress/?json=1 called on a default WordPress installation (formatted for readability): { "status": "ok", "count": 1, "count_total": 1, "pages": 1, "posts": [ { "id": 1, "type": "post", "slug": "hello-world", "url": "http:\/\/localhost\/wordpress\/?p=1", "title": "Hello world!", "title_plain": "Hello world!", "content": "<p>Welcome to WordPress. This is your first post. Edit or delete it, then start blogging!<\/p>\n", "excerpt": "Welcome to WordPress. This is your first post. Edit or delete it, then start blogging!\n", "date": "2009-11-11 12:50:19", "modified": "2009-11-11 12:50:19", "categories": [], "tags": [], "author": { "id": 1, "slug": "admin", "name": "admin", "first_name": "", "last_name": "", "nickname": "", "url": "", "description": "" }, "comments": [ { "id": 1, "name": "Mr WordPress", "url": "http:\/\/wordpress.org\/", "date": "2009-11-11 12:50:19", "content": "<p>Hi, this is a comment.<br \/>To delete a comment, just log in and view the post's comments. There you will have the option to edit or delete them.<\/p>\n", "parent": 0 } ], "comment_count": 1, "comment_status": "open" } ] }<h3>2. Request methods</h3> Request methods are available from the following controllers: Core controller – basic introspection methods Posts controller – data manipulation methods for posts Respond controller – comment/trackback submission methods Widgets controller – retrieve sidebar widgets 2.1. Core controller methods The Core controller offers a mostly-complete set of introspection methods for retrieving content from WordPress. Method: info Returns information about JSON API. Optional arguments controller – returns detailed information about a specific controller Response { "status": "ok", "json_api_version": "1.0", "controllers": [ "core" ] } Response with “controller=core” { "status": "ok", "name": "Core", "description": "Basic introspection methods", "methods": [ ... ] }<h3>Method: get_recent_posts</h3> Returns an array of recent posts. You can invoke this from the WordPress home page either by setting json to a non-empty value (i.e., json=1) or from any page by setting json=get_recent_posts. Optional arguments count – determines how many posts per page are returned (default value is 10) page – return a specific page number from the results post_type – used to retrieve custom post types Response { "status": "ok", "count": 10, "count_total": 79, "pages": 7, "posts": [ { ... }, { ... }, ... ] }<h3>Method: get_posts</h3> Returns posts according to WordPress’s WP_Query parameters. The one default parameter is ignore_sticky_posts=1 (this can be overridden). Optional arguments count – determines how many posts per page are returned (default value is 10) page – return a specific page number from the results post_type – used to retrieve custom post types Further reading See the WP_Query documentation for a full list of supported parameters. The post_status parameter is currently ignored. Response { "status": "ok", "count": 1, "posts": [ { ... } ] }<h3>Method: get_post</h3> Returns a single post object. One of the following is required Invoking the JSON API implicitly (i.e., ?json=1) on a post URL id or post_id – set to the post’s ID slug or post_slug – set to the post’s URL slug Optional arguments post_type – used to retrieve custom post types Response { "status": "ok", "post": { ... } }<h3>Method: get_page</h3> Returns a single page object. One of the following is required Invoking the JSON API implicitly (i.e., ?json=1) on a page URL id or page_id – set to the page’s ID slug or page_slug – set to the page’s URL slug Optional arguments children – set to a non-empty value to include a recursive hierarchy of child pages post_type – used to retrieve custom post types Response { "status": "ok", "page": { ... } }<h3>Method: get_date_posts</h3> Returns an array of posts/pages in a specific date archive (by day, month, or year). One of the following is required Invoking the JSON API implicitly (i.e., ?json=1) on a date archive page date – set to a date in the format YYYY or YYYY-MM or YYYY-MM-DD (non-numeric characters are stripped from the var, so YYYYMMDD or YYYY/MM/DD are also valid) Optional arguments count – determines how many posts per page are returned (default value is 10) page – return a specific page number from the results post_type – used to retrieve custom post types Response { "status": "ok", "count": 10, "count_total": 79, "pages": 7, "posts": [ { ... }, { ... }, ... ] }<h3>Method: get_category_posts</h3> Returns an array of posts/pages in a specific category. One of the following is required Invoking the JSON API implicitly (i.e., ?json=1) on a category archive page id or category_id – set to the category’s ID slug or category_slug – set to the category’s URL slug Optional arguments count – determines how many posts per page are returned (default value is 10) page – return a specific page number from the results post_type – used to retrieve custom post types Response { "status": "ok", "count": 10, "count_total": 79, "pages": 7, "category": { ... } "posts": [ { ... }, { ... }, ... ] }<h3>Method: get_tag_posts</h3> Returns an array of posts/pages with a specific tag. One of the following is required Invoking the JSON API implicitly (i.e., ?json=1) on a tag archive page id or tag_id – set to the tag’s ID slug or tag_slug – set to the tag’s URL slug Optional arguments count – determines how many posts per page are returned (default value is 10) page – return a specific page number from the results post_type – used to retrieve custom post types Response { "status": "ok", "count": 10, "count_total": 79, "pages": 7, "tag": { ... } "posts": [ { ... }, { ... }, ... ] }<h3>Method: get_author_posts</h3> Returns an array of posts/pages written by a specific author. One of the following is required Invoking the JSON API implicitly (i.e., ?json=1) on an author archive page id or author_id – set to the author’s ID slug or author_slug – set to the author’s URL slug Optional arguments count – determines how many posts per page are returned (default value is 10) page – return a specific page number from the results post_type – used to retrieve custom post types Response { "status": "ok", "count": 10, "count_total": 79, "pages": 7, "author": { ... } "posts": [ { ... }, { ... }, ... ] }<h3>Method: get_search_results</h3> Returns an array of posts/pages in response to a search query. One of the following is required Invoking the JSON API implicitly (i.e., ?json=1) on a search results page search – set to the desired search query Optional arguments count – determines how many posts per page are returned (default value is 10) page – return a specific page number from the results post_type – used to retrieve custom post types Response { "status": "ok", "count": 10, "count_total": 79, "pages": 7, "posts": [ { ... }, { ... }, ... ] }<h3>Method: get_date_index</h3> Returns both an array of date page permalinks and a tree structure representation of the archive. Response { "status": "ok", "permalinks": [ "...", "...", "..." ], "tree": { "2009": { "09": 17, "10": 20, "11": 7 } } Note: the tree is arranged by response.tree.[year].[month].[number of posts]. Method: get_category_index Returns an array of active categories. Optional argument parent – returns categories that are direct children of the parent ID Response { "status": "ok", "count": 3, "categories": [ { ... }, { ... }, { ... } ] }<h3>Method: get_tag_index</h3> Returns an array of active tags. Response { "status": "ok", "count": 3 "tags": [ { ... }, { ... }, { ... } ] }<h3>Method: get_author_index</h3> Returns an array of active blog authors. Response { "status": "ok", "count": 3, "authors": [ { ... }, { ... }, { ... } ] }<h3>Method: get_page_index</h3> Returns a hierarchical tree of page posts. Response { "status": "ok", "pages": [ { ... }, { ... }, { ... } ] }<h3>Method: get_nonce</h3> Returns a WordPress nonce value, required to call some data manipulation methods. Required arguments controller – the JSON API controller for the method you will use the nonce for method – the method you wish to call (currently create_post is the only method that requires a nonce) Response { "status": "ok", "controller": "posts", "method": "create_post", "nonce": "cefe01efd4" } Further reading To learn more about how nonces are used in WordPress, see Mark Jaquith’s article on the subject. 2.2. Pages controller methods Method: create_post Creates a new post. Required argument nonce – available from the get_nonce method (call with vars controller=posts and method=create_post) Optional arguments status – sets the post status (“draft” or “publish”), default is “draft” title – the post title content – the post content author – the post’s author (login name), default is the current logged in user categories – a comma-separated list of categories (URL slugs) tags – a comma-separated list of tags (URL slugs) Note: including a file upload field called attachment will cause an attachment to be stored with your new post. Method: update_post Updates a post. Required argument nonce – available from the get_nonce method (call with vars controller=posts and method=update_post) One of the following is required id or post_id – set to the post’s ID slug or post_slug – set to the post’s URL slug Optional arguments status – sets the post status (“draft” or “publish”), default is “draft” title – the post title content – the post content author – the post’s author (login name), default is the current logged in user categories – a comma-separated list of categories (URL slugs) tags – a comma-separated list of tags (URL slugs) Note: including a file upload field called attachment will cause an attachment to be stored with your post. Method: delete_post Deletes a post. Required argument nonce – available from the get_nonce method (call with vars controller=posts and method=delete_post) One of the following is required id or post_id – set to the post’s ID slug or post_slug – set to the post’s URL slug 2.3. Respond controller methods Method: submit_comment Submits a comment to a WordPress post. Required arguments post_id – which post to comment on name – the commenter’s name email – the commenter’s email address content – the comment content Optional arguments redirect – redirect instead of returning a JSON object redirect_ok – redirect to a specific URL when the status value is ok redirect_error – redirect to a specific URL when the status value is error redirect_pending – redirect to a specific URL when the status value is pending Custom status values pending – assigned if the comment submission is pending moderation 2.4. Widgets controller methods Method: get_sidebar Retrieves widgets assigned to a sidebar. Required arguments sidebar_id – the name or number of the sidebar to retrieve 3. Request arguments API requests can be controlled by specifying one of the following arguments as URL query vars. Examples Debug the response: http://www.example.org/api/get_page_index/?dev=1 Widget-style JSONP output: http://www.example.org/api/get_recent_posts/?callback=show_posts_widget&read_more=More&count=3 Redirect on error: http://www.example.org/api/posts/create_post/?callback_error=http%3A%2F%2Fwww.example.org%2Fhelp.html 3.1. Output-modifying arguments The following arguments modify how you get results back from the API. The redirect response styles are intended for use with the data manipulation methods. Setting callback to a JavaScript function name will trigger a JSONP-style callback. Setting redirect to a URL will cause the user’s browser to redirect to the specified URL with a status value appended to the query vars (see the Response objects section below for an explanation of status values). Setting redirect_[status] allows you to control the resulting browser redirection depending on the status value. Setting dev to a non-empty value adds whitespace for readability and responds with text/plain Errors are suppressed unless dev is set to a non-empty value Setting json_encode_options will let you specify an integer bitmask to modify the behavior of PHP’s json_encode (Note: this option is only recognized in PHP version 5.3+) Setting json_unescaped_unicode will replace unicode-escaped characters with their unescaped equivalents (e.g., \u00e1 becomes á) Omitting all of the above arguments will result in a standard JSON response. 3.2. Content-modifying arguments These arguments are available to modify all introspection methods: date_format – Changes the format of date values. Uses the same syntax as PHP’s date() function. Default value is Y-m-d H:i:s. read_more – Changes the ‘read more’ link text in post content. include – Specifies which post data fields to include. Expects a comma-separated list of post fields. Leaving this empty includes all fields. exclude – Specifies which post data fields to exclude. Expects a comma-separated list of post fields. custom_fields – Includes values from posts’ Custom Fields. Expects a comma-separated list of custom field keys. author_meta – Includes additional author metadata. Should be a comma-separated list of metadata fields. count – Controls the number of posts to include (defaults to the number specified by WordPress) order – Controls the order of post results (‘DESC’ or ‘ASC’). Default value is ‘DESC’. order_by – Controls which field to order results by. Expects one of the following values: author date (default value) title modified menu_order (only works with Pages) parent ID rand meta_value (meta_key must also be set) none comment_count meta_key, meta_value, meta_compare – Retrieve posts (or Pages) based on a custom field key or value. 3.3. Using include/exclude and redirects About include/exclude arguments By default you get all values included with each post object. Specify a list of include values will cause the post object to filter out the values absent from the list. Specifying exclude causes post objects to include all values except the fields you list. For example, the query exclude=comments includes everything except the comments. About the redirect argument The redirect response style is useful for when you need the user’s browser to make a request directly rather than making proxy requests using a tool like cURL. Setting a redirect argument causes the user’s browser to redirect back to the specified URL instead of returning a JSON object. The resulting status value is included as an extra query variable. For example calling an API method with redirect set to http://www.example.com/foo will result in a redirection to one of the following: http://www.example.com/foo?status=ok http://www.example.com/foo?status=error You can also set separate URLs to handle status values differently. You could set redirect_ok to http://www.example.com/handle_ok and redirect_error to http://www.example.com/handle_error in order to have more fine-tuned control over the method result. 4. Response objects This section describes data objects you can retrieve from WordPress and the optional URL redirects. Status values All JSON API requests result in a status value. The two basic status values are ok and error. Additional status values are available for certain methods (such as pending in the case of the submit_comment method). API methods that result in custom status values include a custom status values section in their documentation. Naming compatibility Developers familiar with WordPress may notice that many names for properties and arguments have been changed. This was a stylistic choice that intends to provide more clarity and consistency in the interface. 4.1. Post response object id – Integer type – String (e.g., post or page) slug – String url – String title – String title_plain – String content – String (modified by the read_more argument) excerpt – String date – String (modified by the date_format argument) modified – String (modified by the date_format argument) categories – Array of category objects tags – Array of tag objects author Author object comments – Array of comment objects attachments – Array of attachment objects comment_count – Integer comment_status – String ("open" or "closed") thumbnail – String (only included if a post thumbnail has been specified) custom_fields – Object (included by setting the custom_fields argument to a comma-separated list of custom field names) taxonomy_(taxonomy) – Array of custom taxonomy objects (these resemble Category or Tag response objects, depending on whether the taxonomy is hierarchical) Note The thumbnail attribute returns a URL to the image size specified by the optional thumbnail_size request argument. By default this will use the thumbnail or post-thumbnail sizes, depending on your version of WordPress. See Mark Jaquith’s post on the topic for more information. 4.2. Category response object id – Integer slug – String title – String description – String parent – Integer post_count – Integer 4.3. Tag response object id – Integer slug – String title – String description – String post_count – Integer 4.4. Author response object id – Integer slug – String name – String first_name – String last_name – String nickname – String url – String description – String Note: You can include additional values by setting the author_meta argument to a comma-separated list of metadata fields. 4.5. Comment response object id – Integer name – String url – String date – String content – String parent – Integer author – Object (only set if the comment author was registered & logged in) 4.6. Attachment response object id – Integer url – String slug – String title – String description – String caption – String parent – Integer mime_type – String images – Object with values including thumbnail, medium, large, full, each of which are objects with values url, width and height (only set if the attachment is an image) 5. Extending JSON API JSON API exposes several WordPress action and filter hooks as well as a modular controller system for adding new API methods. 5.1. Plugin hooks JSON API exposes several action and filter hooks to augment its behavior. Filter: json_api_controllers This filter controls the array of controllers available to JSON API. The callback function is passed a single argument, an array of strings. Example // Add a custom controller add_filter('json_api_controllers', 'add_my_controller'); function add_my_controller($controllers) { // Corresponds to the class JSON_API_MyController_Controller $controllers[] = 'MyController'; return $controllers; }<h3>Filter: json_api_[controller]_controller_path</h3> Specifies the PHP source file for a given controller, overriding the default location wp-content/plugins/json_api/controllers. Note If you your controller file in the json-api/controllers folder JSON API will find it automatically. Example // Register the source file for JSON_API_Widgets_Controller add_filter('json_api_widgets_controller_path', 'widgets_controller_path'); function widgets_controller_path($default_path) { return '/path/to/widgets.php'; } Capitalization Your filter hook must be all-lowercase to work correctly. The above example would fail with the filter json_api_Widgets_Controller_path, even if that’s how the class is capitalized in the PHP source. Filter: json_api_encode This is called just before the output is encoded into JSON format. The value passed will always be an associative array, according to the format described in each method’s documentation. Those items described in the Response objects section are passed as PHP objects, not associative arrays. Example add_filter('json_api_encode', 'my_encode_kittens'); function my_encode_kittens($response) { if (isset($response['posts'])) { foreach ($response['posts'] as $post) { my_add_kittens($post); // Add kittens to each post } } else if (isset($response['post'])) { my_add_kittens($response['post']); // Add a kittens property } return $response; } function my_add_kittens(&$post) { $post->kittens = 'Kittens!'; }<h3>Action: json_api-[controller]-[method]</h3> Each JSON API method invokes an action when called. Example // Disable get_author_index method (e.g., for security reasons) add_action('json_api-core-get_author_index', 'my_disable_author_index'); function my_disable_author_index() { // Stop execution exit; }<h3>Filter: json_api_http_status</h3> Provides an override for the response HTTP status. Offered for backwards compatibility, since version 1.1.1 and older always returned HTTP 200. Example // Retain old HTTP 200 statuses for legacy support add_filter('json_api_http_status', 'my_http_status'); function my_http_status() { return 200; }<h3>Filter: json_api_query_args</h3> Provides an override for the WP_Query arguments. Example // Allow queries of non-published content add_action('json_api_query_args', 'my_query_args'); function my_query_args($args) { $args['post_status'] = array('draft', 'future', 'publish'); }<h3>Action: json_api_query</h3> Called after the JSON API introspector runs wp_query, passes the WP_Query object as its single argument. 5.2. Developing JSON API controllers Creating a controller To start a new JSON API controller, create a file called hello.php inside wp-content/plugins/json-api/controllers. Add the following class definition: <?php class JSON_API_Hello_Controller { public function hello_world() { return array( "message" => "Hello, world" ); } } ?> Your controller is now available as hello, and exposes one hello_world method. Next, activate your controller from the WordPress admin interface, available from the menu under Settings > JSON API. You can either click on the link to your hello_world method from the admin interface or enter it manually. It should have the form: http://www.example.org/api/hello/hello_world/?dev=1 or http://www.example.org/?json=hello.hello_world&dev=1 (note the use of the dev argument to enable human-readable output). You should get the following output: { "status": "ok", "message": "Hello, world" } Using query vars To customize the behavior of your controller, you will want to make use of the global $json_api->query object. Add the following method to your controller: public function hello_person() { global $json_api; $name = $json_api->query->name; return array( "message" => "Hello, $name." ); } Now append the name query var to the method call: http://www.example.org/api/hello/hello_world/?dev=1&name=Alice or http://www.example.org/?json=hello.hello_world&dev=1&name=Alice. { "status": "ok", "message": "Hello, Alice" } Introspector and data models Your controller can use any of the existing WordPress functions to collect data, but JSON API also includes an introspector that wraps data in objects defined in the json-api/models directory. These are the same data models described in Section 4: Response objects. Here is an example of how you might use the introspector: // Retrieve posts based on custom field key/value pair public function get_custom_posts() { global $json_api; // Make sure we have key/value query vars if (!$json_api->query->key || !$json_api->query->value) { $json_api->error("Include a 'key' and 'value' query var."); } // See also: https://codex.wordpress.org/Template_Tags/query_posts $posts = $json_api->introspector->get_posts(array( 'meta_key' => $json_api->query->key, 'meta_value' => $json_api->query->value )); return array( 'key' => $key, 'value' => $value, 'posts' => $posts ); } External controllers It is recommended that custom controllers are kept outside of json-api/controllers in order to avoid accidental deletion during upgrades or site migrations. To make your controller visible from an external plugin or theme directory you will need to use two filters: json_api_controllers and json_api_[controller]_controller_path. Move the hello.php file from the steps above into your theme’s directory. Then add the following to your theme’s functions.php file (if your theme doesn’t have a file called functions.php you can create one). function add_hello_controller($controllers) { $controllers[] = 'hello'; return $controllers; } add_filter('json_api_controllers', 'add_hello_controller'); function set_hello_controller_path() { return "/path/to/theme/hello.php"; } add_filter('json_api_hello_controller_path', 'set_hello_controller_path');<h3>5.3. Configuration options</h3> The following are constants you can define in your wp-config.php folder: JSON_API_DIR – set to the directory where JSON API plugin lives (in some cases this can be useful for mu-plugins with WordPress MU) JSON_API_CONTROLLERS – a comma-separated list of default controllers to enable (this is overridden by the JSON API settings page) 6. Unit tests JSON API comes with a set of tests that should make it easier to maintain and reveal incompatibilities when they might occur. This is an ongoing process, I hope to improve the test coverage going forward. 6.1. Preparing a WordPress test site There are a few necessary steps that need to be carried out before the test suite will run properly. WordPress should generate a new set of tables before you start, so if you’re testing with a wp_ table prefix make sure the database has no existing tables of this kind Configure and install a new copy of WordPress Delete the Hello World post and Sample Page (titled “About” in some versions of WordPress) Enable user-friendly URLs from Settings > Permalinks, use the “Day and name” format Install + Activate the JSON API plugin and enable all bundled controllers from Settings > JSON API Import the Theme Unit Test test data XML file from Settings > Import > WordPress (you will need to install the WordPress Importer plugin) 6.2. Running the tests From the command line, make sure you have the HTTP_Client PEAR package installed: pear install HTTP_Client Change directory to tests and run the following: pear run-tests You should see the test results print out culminating in a summary: TOTAL TIME: 00:04 23 PASSED TESTS 0 SKIPPED TESTS