reigel_code_002.php

<?php

function reigel_rest_query_vars( $vars ) {
	$vars[] = 'order_location';
	return $vars;
}
add_filter( 'rest_query_vars', 'reigel_rest_query_vars' );

function reigel_rest_post_query( $args, $request ) {
	$parameters = $request->get_query_params();
	
	if (isset($parameters['order_location'])) {
		$args['order_location'] = $parameters['order_location'];
	}
	
	return $args;
}
add_filter('rest_post_query', 'reigel_rest_post_query', 10, 2 );

add_filter( 'posts_fields', 'my_geo_fields', 10, 2 );
add_filter( 'posts_join', 'my_geo_join', 10, 2 );
add_filter( 'posts_orderby', 'my_geo_orderby', 10, 2 );

// filter functions for our query
function my_geo_fields( $fields, $query ) {
	if (isset($query->query_vars['order_location'])) {
		$coords = explode(',', $query->query_vars['order_location']);
		$lat = $coords[0];
		$lon = $coords[1];
		$fields .= ", pm1.meta_value as lat, pm2.meta_value as lon, ACOS(SIN(RADIANS($lat))*SIN(RADIANS(pm1.meta_value))+COS(RADIANS($lat))*COS(RADIANS(pm1.meta_value))*COS(RADIANS(pm2.meta_value)-RADIANS($lon))) * 3959 AS distance";
	}
	return $fields;
}

function my_geo_join( $join, $query ) {
	if (isset($query->query_vars['order_location'])) {
		global $wpdb;
		$join .=	" INNER JOIN $wpdb->postmeta pm1 ON $wpdb->posts.id = pm1.post_id AND pm1.meta_key = 'lat'
			INNER JOIN $wpdb->postmeta pm2 ON $wpdb->posts.id = pm2.post_id AND pm2.meta_key = 'lon' ";
	}
	return $join;
}

function my_geo_orderby( $orderby, $query ) {
	if (isset($query->query_vars['order_location'])) {
		$orderby = 'distance ASC';
	}
	return $orderby;
}
	
function reigel_rest_prepare_post( $response, $post, $request ) {
	$parameters = $request->get_query_params();
	
	if (isset($parameters['order_location'])) {
		$response->data['geolocation'] = array(
			'latitude' 		=> isset($post->lat)?$post->lat:'', 
			'longitude' 	=> isset($post->lon)?$post->lon:'', 
			'distance' 		=> isset($post->distance)?$post->distance:''
		);
	}
	return $response;
}
add_filter( 'rest_prepare_post', 'reigel_rest_prepare_post', 10, 3 );