AJAX search on post pages by custom post type

Instead of 'cat' => 12 and $wp_query use 'category_name' => slug and get_posts().

Here is a basic example how it works:

PHP

add_action( 'wp_loaded', array ( 'T5_Ajax_Search', 'init' ) );

/**
 * Ajaxify the search form.
 */
class T5_Ajax_Search
{
    /**
     * The main instance. You can create further instances for unit tests.
     * @type object
     */
    protected static $instance = NULL;

    /**
     * Action name used by AJAX callback handlers
     * @type string
     */
    protected $action = 't5_ajax_search';

    /**
     * Handler for initial load.
     *
     * @wp-hook wp_loaded
     * @return void
     */
    public static function init()
    {
        NULL === self::$instance and self::$instance = new self;
        return self::$instance;
    }

    /**
     * Constructor. Registers the actions.
     *
     *  @wp-hook wp_loaded
     *  @return object
     */
    public function __construct()
    {
        $callback = array ( $this, 'search' );
        add_action( 'wp_ajax_'        . $this->action,        $callback );
        add_action( 'wp_ajax_nopriv_' . $this->action, $callback );
        add_action( 'wp_enqueue_scripts', array ( $this, 'register_script' ) );
    }

    /**
     * Callback for AJAX search.
     *
     * @wp-hook wp_ajax_t5_ajax_search
     * @wp-hook wp_ajax_nopriv_t5_ajax_search
     * @return void
     */
    public function search()
    {
        $args  = array ( 's' => $_POST['search_term'] );
        $args  = apply_filters( 't5_ajax_search_args', $args );
        $posts = get_posts( $args );
        if ( $posts )
        {
            $this->render_search_results( $posts );
        }
        else
        {
            print '<b>nothing found</b>';
        }
        exit;
    }

    /**
     * Create markup from $posts
     *
     * @param array $posts Array of post objects
     * @return void
     */
    protected function render_search_results( $posts )
    {
        print '<ul class="t5-ajax-search-results">';

        foreach ( $posts as $post )
        {
            printf(
                '<li><a href="https://wordpress.stackexchange.com/questions/62720/%1$s">%2$s</a></li>',
                get_permalink( $post->ID ),
                esc_html( $post->post_title )
            );
        }
        print '</ul>';
    }

    /**
     * Register script and local variables.
     *
     * @wp-hook wp_enqueue_scripts
     * @return void
     */
    public function register_script()
    {
        wp_enqueue_script(
            't5-ajax',
            #plugins_url( __FILE__ ) . '/search.js',
            plugins_url( 'search.js', __FILE__ ),
            array ( 'jquery' ),
            NULL,
            TRUE
        );

        wp_localize_script(
            't5-ajax',
            'T5Ajax',
            array(
                'ajaxurl' => admin_url( 'admin-ajax.php' ),
                'action'  => $this->action
            )
        );
    }
}

JavaScript search.js

jQuery( function( $ ) {
    // search filed
    var $s = $( '#s' );
    // the search form
    var $sForm = $s.closest( 'form' );
    console.log( $sForm );
    $sForm.on( 'submit', function( event) {
        event.preventDefault();
        $.post(
            T5Ajax.ajaxurl,
            {
                action:     T5Ajax.action,
                search_term: $s.val()
            },
            function( response ) {
                // just append the result to the search form.
                $sForm.append( response );
            }
        );
    });
});

Restricting the search

add_filter( 't5_ajax_search_args', 'restrict_t5_search' );

function restrict_t5_search( $args )
{
    $args['post_type'] = array ( 'post', 'fod_videos' );
    $args['category_name']       = 'category-slug';
    return $args;
}

Instead of my $this->render_search_results( $posts ); you can also load a template from your theme and use the $posts array in a more sophisticated result. 🙂