Sergiy Dzysyak

This plugin provides simple REST API for the popular search <a href="https://wordpress.org/" title="Your favorite blogging software" rel="ugc">WordPress</a> search engine – <a href="https://wordpress.org/plugins/relevanssi/" title="A Better Search" rel="ugc">Relevanssi</a>.
As far as this plugin provides API for the Relevanssi plugin, it should be installed.
Key features
<ul>
<li>Search through posts of a certain type. By default all types.</li>
<li>Results in pagination and optional.</li>
<li>Sets X-WP-Total header with a total number of records, the same way as the default search API does.</li>
<li>Sets X-WP-TotalPages header with a total number of pages, the same way as the default search API does.</li>
<li>Multilingual websites support. Both WPML and Polylang are supported, but not tested well, so let me know if you will find any problems.</li>
<li>Taxonomy filters are supported now. Some features may be missed, so feel free to report them.</li>
<li>Ordering option added. It is also possible to order by meta_key/meta_value/meta_value_num. </li>
</ul>
Brief usage examples
<ul>
<li>https://[your domain]/wp-json/relevanssi/v1/search?keyword=query</li>
<li>https://[your domain]/wp-json/relevanssi/v1/search?keyword=query&per_page=5</li>
<li>https://[your domain]/wp-json/relevanssi/v1/search?keyword=query&per_page=5&page=2</li>
</ul>
Define post type:
<ul>
<li>https://[your domain]/wp-json/relevanssi/v1/search?keyword=query&per_page=5&page=2&type=post</li>
</ul>
Filter by taxonomy/taxonomies:
<ul>
<li>https://[your domain]/wp-json/relevanssi/v1/search?keyword=test&tax_query[0][taxonomy]=category&tax_query[0][field]=id&tax_query[0][terms]=3</li>
<li>https://[your domain]/wp-json/relevanssi/v1/search?keyword=test&tax_query[relation]=AND&tax_query[0][taxonomy]=category&tax_query[0][field]=id&tax_query[0][terms]=3&tax_query[1][taxonomy]=category&tax_query[1][field]=id&tax_query[1][terms]=2</li>
</ul>
Exclude category via taxonomies:
<ul>
<li>https://[your domain]/wp-json/relevanssi/v1/search?keyword=test&tax_query[0][taxonomy]=category&tax_query[0][field]=id&tax_query[0][terms]=3&tax_query[0][operator]=NOT IN</li>
</ul>
For multilingual websites (WPML & Polylang):
<ul>
<li>
https://[your domain]/wp-json/relevanssi/v1/search?keyword=query&lng=en
<ul>
<li>Results in order:</li>
</ul>
</li>
<li>
https://[your domain]/wp-json/relevanssi/v1/search?keyword=test&type=post&orderby=modified&order=DESC
</li>
<li>https://[your domain]/wp-json/relevanssi/v1/search?keyword=test&type=post&orderby=modified&order=ASC</li>
<li>https://[your domain]/wp-json/relevanssi/v1/search?keyword=test&type=post&meta_key=some_key&orderby=meta_value|meta_value_num&order=ASC</li>
</ul>
Demo website
You can try the plugin on our demo website http://demo.erlycoder.com/demo1/. For example, you can try the following request:
Basic: 
<a href="http://demo.erlycoder.com/demo1/wp-json/relevanssi/v1/search?keyword=test" rel="nofollow ugc">http://demo.erlycoder.com/demo1/wp-json/relevanssi/v1/search?keyword=test</a>
Order posts by modification time: 
<a href="http://demo.erlycoder.com/demo1/wp-json/relevanssi/v1/search?keyword=test&type=post&orderby=modified&order=DESC" rel="nofollow ugc">http://demo.erlycoder.com/demo1/wp-json/relevanssi/v1/search?keyword=test&type=post&orderby=modified&order=DESC</a> 
<a href="http://demo.erlycoder.com/demo1/wp-json/relevanssi/v1/search?keyword=test&type=post&orderby=modified&order=ASC" rel="nofollow ugc">http://demo.erlycoder.com/demo1/wp-json/relevanssi/v1/search?keyword=test&type=post&orderby=modified&order=ASC</a>
Filter posts by taxonomy (one single category): 
<a href="http://demo.erlycoder.com/demo1/wp-json/relevanssi/v1/search?keyword=test&tax_query[0][taxonomy]=category&tax_query[0][field]=id&tax_query[0][terms]=3" rel="nofollow ugc">http://demo.erlycoder.com/demo1/wp-json/relevanssi/v1/search?keyword=test&tax_query[0][taxonomy]=category&tax_query[0][field]=id&tax_query[0][terms]=3</a>
Filter posts by taxonomy (exclude category): 
[http://demo.erlycoder.com/demo1/wp-json/relevanssi/v1/search?keyword=test&tax_query[0][taxonomy]=category&tax_query[0][field]=id&tax_query[0][terms]=3&tax_query[0][operator]=NOT IN](http://demo.erlycoder.com/demo1/wp-json/relevanssi/v1/search?keyword=test&tax_query[0][taxonomy]=category&tax_query[0][field]=id&tax_query[0][terms]=3&tax_query[0][operator]=NOT IN)

REST API for Relevanssi

Nice and simple plugin

The plugin provides a REST API endpoint for the Relevanssi search plugin.

jamesdlow

Extensions to WordPress wp-json for the PageApp API and mobile framework: 
* Whitelist meta values for the WordPress rest api 
* Enable Relevanssi over the WordPress rest api 
* PageApp compatiable API using wp-json 
* Helper functions and utilities

PageApp

Extensions to Wordpress wp-json for the PageApp API and mobile framework

REST API for Relevanssi vs PageApp