WordPress: Create a REST API endpoint

page-api.php

<?php 
/*
* Sample code for using WordPress as a REST API endpoint (vs AJAX Admin)
* Author: Pete Nelson @GunGeekATX
*
* 1) Create a page called API in WordPres
* 2) Create a file called page-api.php in your theme directory
* 3) Add code as-needed
*
*/


// See what API call we want to do
// example: http://localhost:/wp-mysite/api/?action=list-all-pages

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

$output = null;
$sample_api = new My_Sample_API();

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

if ($output) {
	// callback support for JSONP
	if (isset($_REQUEST["callback"])) {
		header("Content-Type: application/javascript");
		echo $_REQUEST['callback'] . '(' . json_encode($output) . ')';
	}
	else {
		header("Content-Type: application/json");
		echo json_encode($output);
	}
}

die();



class My_Sample_API {

	function list_all_pages() {

		// last three options are from 
		// http://www.billerickson.net/code/improve-performance-of-wp_query/

		$query = new WP_Query(
			array(
				'post_type' => 'page',
				'no_found_rows' => true, // counts posts, remove if pagination required
				'update_post_term_cache' => false, // grabs terms, remove if terms required (category, tag...)
				'update_post_meta_cache' => false, // grabs post meta, remove if post meta required			
			)
		);

		$output = array();

		// output just a small subset of the page information
		while ($query->have_posts()) {
			$p= $query->next_post();

			// we'll return just a subest of
			$output[] = array(
				'id' => $p->ID,
				'title' => $p->post_title,
				'post_date_gmt' => $p->post_date_gmt,
				'permalink' => get_permalink( $p->ID ),
			);

		}

		return $output;

	}

}

Is it possible they changed the admin-ajax.php which stopped the autocomplete..