An Ajax Request via WP Rest

new-ajax-request.php

<?php
/**
 * register the API route
 *
 * @since 0.9
 **/
add_action( 'rest_api_init', 'dn_rest_routes' );
function dn_rest_routes() {
	register_rest_route(
		'buddypress-desktop-notification/v1', '/notifications/',
		array(
			'methods' 				=> WP_REST_Server::READABLE,
			'callback' 				=> 'dn_query',
			'args'					=> array(
					'since'			=> array(
						'validate_callback'	=> 'dn_strtotime',
					),
				),
			'permission_callback' 	=> 'is_user_logged_in',
		)
	);
}

/**
 * Validate 'since' parameter
 * @since 0.9
 *
 * @param  (string) $data 	the data string to validate
 * @param  (object) $rest 	the rest response object
 * @param  (string) $key 		the argument key
 *
 * @return (boolean) 	valide or invalid
 **/
function dn_strtotime( $data, $rest, $key ) {
	if ( 'since' === $key ) {
		return strtotime( $data );
	}
	return false;
}

/**
 * dn_query()
 * Checks for new messages to send
 *
 * @since  0.6
 * @param  (array) 	$data 	The REST API data
 * @return (array) 	$entries The REST return
 **/
function dn_query( $data ) {
	$entries = array();
	$entries = dn_messages_query();
	if ( count( $entries ) === 0 ) {
		$entries = dn_notifications_query();
	}
	if ( count( $entries ) === 0 ) {
		$entries = dn_activities_query( $data );
	}

	return apply_filters( 'dn_entries', $entries );
}

?>