Magento2 API – Get Categories and Subcategories via REST API

Should try with Search using REST APIs: http://devdocs.magento.com/guides/v2.1/howdoi/webapi/search-criteria.html

You should try with GET:

http://{magento_host}/rest/V1/products? searchCriteria[filter_groups][0][filters][0][field]=featured& searchCriteria[filter_groups][0][filters][0][value]=0 searchCriteria[filter_groups][0][filters][0][condition_type]=eq

<?php

$userData = ["username" => "admin", "password" => "admin123"];

$ch = curl_init("http://mage215.loc/rest/V1/integration/admin/token");
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($userData));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-Type: application/json", "Content-Lenght: " . strlen(json_encode($userData))));

$token = curl_exec($ch);



$ch = curl_init("http://mage215.loc/rest/V1/products?
searchCriteria[filter_groups][0][filters][0][field]=featured&
searchCriteria[filter_groups][0][filters][0][value]=0
searchCriteria[filter_groups][0][filters][0][condition_type]=eq");

curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "GET"); //  method
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
//curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($emailcontent));
curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-Type: application/json", "Authorization: Bearer " . json_decode($token)));

$result = curl_exec($ch);

$result = json_decode($result, 1);
echo '<pre>';print_r($result);

https://domain.com/index.php/rest/V1/orders?searchCriteria[f‌​ilter_groups][0][fil‌​ters][0][field]=cust‌​omer_email&searchCri‌​teria[filter_groups]‌​[0][filters][0][valu‌​e]=aaa@google.com&se‌​archCriteria[filter_‌​groups][0][filters][‌​0][condition_type]=e‌​q&searchCriteria[fil‌​ter_groups][1][filte‌​rs][0][field]=status‌​&searchCriteria[filt‌​er_groups][1][filter‌​s][0][value]=pending‌​&searchCriteria[filt‌​er_groups][1][filter‌​s][0][condition_type‌​]=eq