get_categories order by meta key issue?

Question

I'm trying to search for a way to order categories by meta value. From what I read, it seems like I can use:

get_categories('child_of=92&hide_empty=false&orderby=meta_value&meta_key=date&order=ASC');

However, this does not work at all, the categories are still not in the order I want. I wonder how I can:

1. correct this to make it work
2. print out the sql to see what is really going on inside?

Thank you very much in advance.

Answer 1

You can also give the get_categories new meta and sort using usort.

$subcategories = get_categories();

foreach ($subcategories as $subcategory) {
$subcategory->your_meta_key = your_meta_value;
}

foreach ($subcategories as $subcategory) {
blah blah blah
}

function my_cmp($a, $b) {
if ($a->ordering == $b->ordering) {
return 0;
}
return ($a->ordering < $b->ordering) ? -1 : 1;
}


usort($subcategories, "my_cmp");

Answer 2

First of all, I must mention that I'm using the module custom category fields, and second of all I'm a complete WP newbie

Anyhow, after learning that this cannot be done by default, I looked into the get_categories functions and finally came up with a solution

function category_custom_field_get_terms_orderby( $orderby, $args ){
    if($args['orderby'] == 'category_custom_field' && isset($args['category_custom_field'])) 
        return 'cv.field_value';
    return $orderby;
}

function category_custom_field_get_terms_fields( $selects, $args ){
    if($args['orderby'] == 'category_custom_field' && isset($args['category_custom_field']))
        $selects[] = 'cv.*';
    return $selects;
}

function category_custom_field_terms_clauses($pieces, $taxonomies, $args){
    global $wpdb;
    if($args['orderby'] == 'category_custom_field' && isset($args['category_custom_field']))
        $pieces['join'] .= " LEFT JOIN $wpdb->prefix" . "ccf_Value cv ON cv.term_id = tt.term_id AND cv.field_name = '".$args['category_custom_field']."'";
    return $pieces;
}    

add_filter('get_terms_orderby', 'category_custom_field_get_terms_orderby',1,2);

add_filter('get_terms_fields', 'category_custom_field_get_terms_fields',1,2);

add_filter('terms_clauses', 'category_custom_field_terms_clauses',1,3);

(The code above can be put into the theme functions.php file)

then the code to get categories is:

get_categories('child_of=92&hide_empty=false&orderby=category_custom_field&category_custom_field=date&order=DESC');

Any correction is greatly appreciated!