Filtering Posts by Multiple Taxonomy Terms such as in an Admin Post Listing?

2 comments

1. I don’t have the time to actually write up a fully working example for you right now, but since you requested help in email I figured I would point you in the right direction.

   As you may or may not know, this isn’t really an issue for the admin post listing; most all of that code should work fine. The issue is that currently WordPress does not have the ability to use query_posts()/get_posts()/WP_Query to filter on more than one taxonomy term without using hooks. (There is a very good chance that will change in v3.1; we can only hope!)

   The solution is to use a 'posts_where' hook as illustrated here with the tax_terms_where() function written for that answer:

   • Getting the Intersection of Two Custom Taxonomy Terms for a Custom Post Type?

   You’ll also need to modify the 'parse_query' hook to capture your filter values, something like this (I have not tested this, so there may be small syntax errors):

   <?php
   add_filter('parse_query','yoursite_parse_query');
   function yoursite_parse_query($query) {
     global $pagenow;
     $qv = &$query->query_vars;
     if ($pagenow=='edit.php') {
       $tax_terms = array();
       if (!empty($qv['marka'])) 
         $tax_terms[] = "marka:{$qv['marka']}";
       if (!empty($qv['konu'])) 
         $tax_terms[] = "konu:{$qv['konu']}";
       if (count($tax_terms)) 
         $qv['tax_terms'] = implode(',',$tax_terms);
     }
   }
   

   The above assumes you have dropdowns with names of 'marka' and 'konu'. You’ll probably also need to tell WordPress to recognize them as query vars using an 'admin_init' hook. Again, I haven’t tested this so I’m hoping it works as written:

   add_action('init','yoursite_init');
   function yoursite_init() {
     global $wp;
     $wp->add_query_var('marka');
     $wp->add_query_var('konu');
   }
   

   That’s about it. Combine the knowledge of the three posts; this one, the one on admin lists, and the one on multiple taxonomy queries and I think you’ll get it done. You might even want to post your solution for others to learn from. Let me know if you get stuck.

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2. Late answer

   Update for WordPress 3.5+

   I wrote the following plugin to extend the WP_List_Tables for built in and custom post types with the following features:

   • Add column (if show_admin_column is set to false)
   • Add the taxons incl. links to the table cell
   • Add a dropdown that shows the amount of posts assigned to the taxon to filter the displayed posts
   • Allow for filtering by more than one taxonomy

   Here’s the plugin (best served as mu-plugin):

   add_action( 'plugins_loaded', array( 'WCM_Admin_PT_List_Tax_Filter', 'init' ) );
   class WCM_Admin_PT_List_Tax_Filter
   {
       private static $instance;
   
       public $post_type;
   
       public $taxonomies;
   
       public $new_cols = array();
   
       static function init()
       {
           null === self :: $instance AND self :: $instance = new self;
           return self :: $instance;
       }
   
       public function __construct()
       {
           add_action( 'load-edit.php', array( $this, 'setup' ) );
       }
   
       public function setup()
       {
           add_action( current_filter(), array( $this, 'setup_vars' ), 20 );
           add_action( 'restrict_manage_posts', array( $this, 'get_select' ) );
           add_filter( "manage_taxonomies_for_{$this->post_type}_columns", array( $this, 'add_columns' ) );
       }
   
       public function setup_vars()
       {
           $this->post_type  = get_current_screen()->post_type;
           $this->taxonomies = array_diff(
                get_object_taxonomies( $this->post_type )
               ,get_taxonomies( array( 'show_admin_column' => 'false' ) )
           );
       }
   
       public function add_columns( $taxonomies )
       {
           return array_merge(
                $taxonomies
               ,$this->taxonomies
           );
       }
   
       /**
        * Select form element to filter the post list
        * @return string HTML
        */
       public function get_select()
       {
           $html = '';
           foreach ( $this->taxonomies as $tax )
           {
               $options = sprintf(
                '<option value="">%s %s</option>'
               ,__( 'View All' )
                   ,get_taxonomy( $tax )->label
               );
               $class = is_taxonomy_hierarchical( $tax ) ? ' class="level-0"' : '';
               foreach ( get_terms( $tax ) as $taxon )
               {
                   $options .= sprintf(
                        '<option %s%s value="%s">%s%s</option>'
                       ,isset( $_GET[ $tax ] ) ? selected( $taxon->slug, $_GET[ $tax ], false ) : ''
                       ,'0' !== $taxon->parent ? ' class="level-1"' : $class
                       ,$taxon->slug
                       ,'0' !== $taxon->parent ? str_repeat( '&nbsp;', 3 ) : ''
                       ,"{$taxon->name} ({$taxon->count})"
                   );
               }
               $html .= sprintf(
                   '<select name="%s" id="%s" class="postform">%s</select>'
                   ,$tax
                   ,$tax
                   ,$options
               );
           }
   
           return print $html;
       }
   }
   

   Explanation

   First I did an awesome, but large work-around to get the custom columns in (didn’t know about the 3.5 update for show_admin_column). Then I did a lot to parse_query to get it filter by two taxonomies. Luckily I instantly had a surprising result (with no code added). Look at the following example dump:

     public 'tax_query' => 
       object(WP_Tax_Query)[429]
         public 'queries' => 
           array (size=2)
             0 => 
               array (size=5)
                 'taxonomy' => string 'post_format' (length=11)
                 'terms' => 
                   array (size=1)
                     0 => string 'post-format-gallery' (length=19)
                 'include_children' => boolean true
                 'field' => string 'slug' (length=4)
                 'operator' => string 'IN' (length=2)
             1 => 
               array (size=5)
                 'taxonomy' => string 'category' (length=8)
                 'terms' => 
                   array (size=4)
                     0 => int 5
                     1 => int 6
                     2 => int 7
                     3 => int 8
                 'include_children' => boolean false
                 'field' => string 'term_id' (length=7)
                 'operator' => string 'IN' (length=2)
         public 'relation' => string 'AND' (length=3)
   

   WP already does this by default!

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