page-api.php

<?php 
/*
  Using WordPress as a REST API endpoint (vs AJAX Admin)
  -- with caching using the Transient API --

  forked from: Pete Nelson @GunGeekATX

  1) Create a page called API in WordPres
  2) Create a file called page-api.php in your theme directory
  3) Build custom endpoints
  
*/

// Call the API by sending a POST request to this page, with an 'action' parameter

// from Angular, which sends POST requests in JSON format:
// $http.post('http://localhost/wp-mysite/api', { action: 'home' })

$postdata = file_get_contents("php://input");
$request = json_decode($postdata);

// from anything else that sends its POST requests old school:
// POST http://localhost/wp-mysite/api/?action=list-all-pages
// $.post('http://localhost/wp-mysite/api', {action:'list-all-pages'})

// $action = isset($_REQUEST['action']) ? $_REQUEST['action'] : '';

$output = null;
$api = new API();

switch ($action) {

  case 'list-all-pages':
    $output = $api->list_all_pages();
    break;
  
  default:
    $output = array('error' => 'invalid action');
    break;
}

if ($output) {
  header("Content-Type: application/json");
  echo json_encode($output);
}

die();

// ********************************************************

class API {

  function cached_hello_world(){

    $KEY = "hello_world";

    // try to fetch the response from cache
    // this will fail if the cache is out of date
    $response = get_transient($KEY);
    if($response) return json_decode($response);

    // build our response
    $response = new stdClass();
    $response->data = 'Hello World!';

    // save response to cache, with an expiry date (HOUR_IN_SECONDS)
    set_transient($KEY, json_encode($response), HOUR_IN_SECONDS);

    return $response;

  }

}