autosearch.php

<?php
function autosearch_metabox_callback() {
	$output = '<div id="added-posts"><ul><input type="hidden" value=" " id="autosearch_posts" name="autosearch_posts" /></ul></div>';
	$output .= '<label for="autosearch" id="autosearch-label" >';
	$output .= '<input type="text" id="autosearch" name="autosearch" size="80" />';

	echo $output;
}

add_action( 'add_meta_boxes', 'wp_autosearch_add_metabox' );

function myprefix_autocomplete_suggestions(){
	// Query for suggestions
	$args = array(
		's' => $_REQUEST['term']
	);

	$search_results = new WP_Query( $args );
	// Initialise suggestions array
	$suggestions = array();
	$posts = $search_results->get_posts();
	global $post;
	foreach ($posts as $post) {
		// Initialise suggestion array
		$suggestion = array();
		$suggestion['label'] = get_the_title();
		$suggestion['link'] = get_permalink();
		$suggestion[ 'id' ] = get_the_ID();

		// Add suggestion to suggestions array
		$suggestions[]= $suggestion;
	}
	wp_reset_postdata();
	// JSON encode and echo
	$response = $_GET["callback"] . "(" . json_encode($suggestions) . ")";
	echo $response;

	// Don't forget to exit!
	exit;
}
add_action( 'wp_ajax_myprefix_autocompletesearch', 'myprefix_autocomplete_suggestions' );