Sort posts by custom field numeric value using dropdown

3 comments

1. 'meta_value_num' is not magic, it casts a value as numeric, however, to be properly cast as numeric, a value must be numeric compatible.

   In OP it’s said that the field values are “numeric” but I bet there’s something not numeric, e.g. a currency symbol like “10 $” or “$ 10.00”, or other symbol like “10-“.

   Also consider that using a thousands separator most probably makes the casting fail, because MySQL can mistake it as a decimal separator.

   When you want to use a meta field for order, follow these rules:

   • Do not use any other char that is not numeric (no currency or other symbols, no spaces..)
   • Do not use any thousands separators
   • When a value is an integer (no decimal) do not use a decimal, e.g. if a value is 10, do not use 10.00
   • Use the dot as a decimal separator.

   If you follow previous rules, the order by 'meta_value_num' will work as expected.

   If you are asking yourself how to properly format a price entered using previous rules, the answer is number_format.

   As example, in Italy, a properly formatted price is € 1.000,50 (one thousand euros and fifty cents).

   Following previous rules, one should enter that price as 1000.50

   To output the proper formatted price it’s possible to use a custom function like this:

   function formatted_price( $number ) {
       // force 2 decimals, comma as decimal separator and dot as thousands separator
       return '€ ' . number_format ( (float) $number, 2, ",", "." );
   }
   

   And use it like so:

   while ( have_posts() ) :
       the_post();
   
       if ( $price = get_post_meta( get_the_ID(), 'property_price', TRUE ) ) {
           // assuming the price is stored in the 'property_price' custom field
           echo formatted_price( $price );
       }
   

   ---

   That said, I strongly suggest you avoid the usage of query_posts and replace it with a function hooked into 'pre_get_posts'.

   From Codex:

   … It is inefficient (re-runs SQL queries) and will outright fail in some
   circumstances (especially often when dealing with posts pagination).
   Any modern WP code should use more reliable methods, like making use
   of pre_get_posts hook, for this purpose.

   So, remove any code from your category.php and in your functions.php write:

   add_action( 'pre_get_posts', 'order_properties_by_price' );
   
   function order_properties_by_price( $query ) {
       if ( is_admin() || ! $query->is_main_query() || ! $query->is_category( 'property' ) )
           return;
       $byprice = filter_input( INPUT_GET, 'orderby', FILTER_SANITIZE_STRING ); 
       if ( empty( $byprice ) )
           return;
       if ( $byprice === 'price' ) {
           $order = strtoupper( filter_input( INPUT_GET, 'order', FILTER_SANITIZE_STRING ) ); 
           if ( $order !== 'DESC' ) $order = 'ASC';
           $query->set( 'meta_key', 'property_price' );
           $query->set( 'orderby', 'meta_value_num' );
           $query->set( 'order', $order );
       }
   }
   

   Now, assuming that your ‘property’ archive URL is

   http://www.example.com/category/property/
   

   it will, of course, show posts in category ‘property’ ordered by date (newer to older).

   Using the code posted above, the URL

   http://www.example.com/category/property/?orderby=price
   

   will show posts in category ‘property’ ascending, ordered by price, and the URL

   http://www.example.com/category/property/?orderby=price&order=DESC
   

   will show posts in category ‘property’ descending, ordered by price.

   So, what you need to do, is to make a dropdown that redirects the page to the proper URLs.

   You can write a custom function to output the dropdown:

   function order_properties_menu() {
       if ( ! is_category('property') ) return;
       $url = get_category_link( get_term_by( 'slug', 'property', 'category' ) );
       $form = '<form id="orderbyprice" action="#" method="GET">'
           . '<label>Order by:</label><select name="order">';
       $htl = esc_url( add_query_arg( array( 'orderby' => 'price', 'order' => 'DESC' ), $url ) ) ;
       $lth = esc_url( add_query_arg( array('orderby' => 'price', 'order' => 'ASC' ), $url ) );
       $options = array(
           'latest' => array( 'Latest', $url ),
           'htl'    => array( 'Price High to Low', $htl ),
           'lth'    => array( 'Price Low to High', $lth ) 
       );
       $format = '<option value="%s"%s>%s</option>';
       foreach( $options as $id => $option ) {
           $sel = 'latest';
           if ( get_query_var( 'orderby' ) === 'meta_value_num' )
               $sel = get_query_var( 'order' ) === 'DESC' ? 'htl' : 'lth';
           $selected = selected( $sel, $id, FALSE );
           $form .= sprintf( $format, esc_url( $option[1] ), $selected, esc_html( $option[0] ) );
       }
       echo $form . '</select></form>';
       ?>
       <script>
           jQuery(document).on( 'change', '#orderbyprice select', function() {
               window.location.href = jQuery(this).val();
           });
       </script>
       <?php
   }
   

   This function outputs a dropdown menu that allow users to choose from the 3 ordering options, and when one is selected, the page is redirected accordingly.

   After having added this function in functions.php, put it everywhere you want in your category.php

   order_properties_menu();
   

   and the select will be shown.

   Note that the order_properties_menu() function requires jQuery.

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2. You are doing a few things in a not so ideal way. So here is how to solve your problem.

   1. Create a category-property.php template file

   Paste a standard WordPress loop in this file. If you visit the Property category in your site, you should only see the posts filed in this category, sorted by date (newest to oldest).

   By using the Template Hierarchy (http://codex.wordpress.org/Template_Hierarchy), we now have a page that displays the posts we want.

   If you install the Debug Bar Plugin (http://wordpress.org/extend/plugins/debug-bar/) you can verify that category-property.php is used for this query.

   2. Modify the main query via the pre_get_posts filter

   If you use query_posts(), this runs an additional query to the main query, which is not only a waste of resources, but also results in plenty of problems with pagination not working etc..

   So what we’ll do is write a function (that needs to be in functions.php) that alters the main query on a specific page to sort by the order that we want.

   function my_prefix_sort_property_category( $query ) {
       // if we're not in the admin, and it's the main query, and it's a property category
       if ( ! is_admin() && $query->is_main_query() && is_category( 'Property' ) ) {
           // then modify the main query
           $query->set( 'meta_key', 'property_price' );
           $query->set( 'orderby', 'meta_value_num' );
           $query->set( 'order', 'ASC' );
       }
   }
   add_action( 'pre_get_posts', 'my_prefix_sort_property_category' );
   

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3. i had this problem once, i believe you custom fiel is not set as INT right? for meta_value_num work it should be in INT, not in string, even that you write only numbers in it

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