WordPress: AJAX action to return posts by taxonomy term

ajax-posts-by-taxonomy.php

<?php 
/*
Plugin Name: GGA - AJAX Posts by Taxonomy
Author: Pete Nelson (@GunGeekATX)
Description: <a href="http://petenelson.com/wp-admin/admin-ajax.php?action=gga_posts_by_taxonomy&post_type=post&taxonomy=post_tag&term=android">Try it out</a>
Version: 1.0
*/

/*
http://petenelson.com/wp-admin/admin-ajax.php?action=gga_posts_by_taxonomy&post_type=post&taxonomy=post_tag&term=android
*/


add_action('wp_ajax_gga_posts_by_taxonomy', 'gga_posts_by_taxonomy');
add_action('wp_ajax_nopriv_gga_posts_by_taxonomy', 'gga_posts_by_taxonomy');
function gga_posts_by_taxonomy() {

	$results = new stdClass();
	$results->posts = array();

	$post_type = isset($_REQUEST['post_type']) ? $_REQUEST['post_type'] : '';
	$taxonomy = isset($_REQUEST['taxonomy']) ? $_REQUEST['taxonomy'] : '';
	$taxonomy_term = isset($_REQUEST['term']) ? $_REQUEST['term'] : '';

	if (empty($post_type))
		$post_type == 'post';

	$query_args = array(
		'post_type' => $post_type,
		'posts_per_page' => -1,
	);


	if (!empty($taxonomy) && !empty($taxonomy_term)) {
		$query_args['tax_query'] = array(
			array(
				'taxonomy' => $taxonomy,
				'field' => 'slug',
				'terms' => $taxonomy_term,
			)
		);
	}


	global $post;
	$query = new WP_Query($query_args);

	while ($query->have_posts()) {
		$query->the_post();

		$results->posts[] = array(
			'id' => $post->ID,
			'permalink' => get_permalink( $post->ID ),
			'post_title' => get_the_title( $post->ID ),
			'post_name' => $post->post_name
		);

	}

	wp_reset_query();

	header('Content-Type: application/json');
	echo json_encode($results);
	die();

}