How to create Custom Taxonomy Search Drop Down for specific Post Type

Question

I have a number of custom post types which share a custom taxonomy.

I'm trying to implement a dropdown search box using php (to insert into a widget or elsewhere) that allows selection of a taxonomy term, and returns the posts which have that term, but only within a specific post type.

I'm hoping to then create one of these dropdown search boxes for each post type so a user can easily navigate to posts under a taxonomy term and within a post type.

Can anyone assist with this please?

Answer 1

First create a function to display your search form

function display_custom_search_form($atts){
    $return = '<form role="search" method="get" id="searchform" action="'.home_url( '/' ).'">
                    <div><label class="screen-reader-text" for="s">Search for:</label>
                    '.wp_dropdown_categories(array('name' =>'taxTerm', 'taxonomy' => 'TAXONOMY_NAME').'

    <!-- this is the magic field you will need to change in order for this to work with each post types--->

                        <input type="hidden" name="post_type" value="post" />

                        <input type="submit" id="searchsubmit" value="Search" />
                        <input type="hidden" name="custom_search" value="1"> 
                    </div>
                </form>';
    if ($echo){
        echo $return;
    }else{
        return $return;
    }
}

hook this function as a shortcode so you could use it anywhere you want (post/page/widget)

add_shortcode('my_c_s','display_custom_search_form');
add_filter('widget_text', 'do_shortcode');

then you check if the form is submitted and if so you can filter the posts based on that:

//was the form submitted

if (isset($_GET['custom_search']) && $_GET['custom_search'] == 1){
    add_filter('pre_get_posts','Custom_Search_Filter');
}

 //function to actually filter the posts based on the taxonomy term and post type
function Custom_Search_Filter($query) {
    //only do this on search
    if (is_search()){
        //first check for the first type if not set then its the default post.
        $post_type = $_GET['post_type'];
        if (!$post_type) {
            $post_type = 'post';
        }
        $query->set('post_type', $post_type);

        //then check for the taxonomy term
        if (isset($_GET['taxTerm'])){
            $query->set('TAXONOMY_NAME', $_GET['taxTerm']);
        }
    }

    return $query;
}  

copy all of the code in to you theme's functions.php and change TAXONOMY_NAME to your actual custom taxonomy name (its there twice).

open your widgets panel and add a simple text widget with [my_c_s] inside and save.