If you are interested in expanding your post, page, or link administration panel, visit this step by step tutorial. Here, we describe how to add new Edit Category fields.
The easiest way to add new Category fields is by using the edit_category_form_fields action hook (line 2). This hook calls your_input_box function during rendering of the WordPress Edit Category page. Just add the hook into the functions.php file of your WordPress theme or plugin.
add_action ( 'edit_category_form_fields', 'your_input_box');
The your_input_box function is used to render additional category input fields. In the function below, we add a drop-down menu containing all the terms for our new Category theme attribute.
function your_input_box($category) {
// Get all themes - the hide_empty argument enables you to get all the terms in your 'theme' taxonomy even the empty ones
$themes = get_terms('theme', 'hide_empty=0');
?>
<tr class="form-field">
<th scope="row" valign="top"><label for="category_theme"><?php _e('Category Theme') ?></label></th>
<td>
<select name='category_theme' id='category_theme' onchange="themeChange()">
<!-- Get all themes and display them as options -->
<?php
foreach ($themes as $theme) {
echo "<option class='theme-option' value='" . $theme->name . "'>" . $theme->name . "</option>\n";
}
?>
</select>
</td>
</tr>
<?php
}
What we would like now, is to have a hook into the Edit Category save function so that we can attach our new attribute to the WordPress Category object.
The WordPress Category object is a WordPress taxonomy object. As of WordPress release 2.8.4, there is no core way to expand taxonomy objects with additional attributes.
There are plugins that try to provide this functionality, but they may not work on WordPress 2.9. In addition, if you are planning to release your theme or plugin, you may not want to tie your code to functions that are not in the WordPress core system.
Since we cannot easily add a new attribute to the Category taxonomy object, we can use the existing category_description attribute to piggyback our new data. One way to achieve this, is to attach JavaScript code to our drop-down menu in the your_input_box function. We do this by adding an onchange attribute to our select form.
<select name='category_theme' id='category_theme' onchange="themeChange()">
Next, we add the following JavaScript before this HTML statement –
<tr class="form-field">
<script type='text/javascript'>
function themeChange() {
// Get category description
var desc = document.getElementById('category_description').value;
var theme = document.getElementById('category_theme').value;
// Piggy-back theme in category description
var startPos = desc.indexOf("SHIBA THEME: ");
if (startPos >= 0) {
var stopPos = desc.indexOf("]", startPos);
var oldTheme = desc.substring(startPos, stopPos);
var newTheme = "SHIBA THEME: " + theme;
desc = desc.replace(oldTheme, newTheme);
} else {
desc = desc + "\n[SHIBA THEME: " + theme + "]";
}
jQuery('#category_description').val(desc);
}
</script>
This JavaScript code will automatically add our new category theme attribute into the existing category_description field so that we may later retrieve it for processing.
By using the WordPress edit_category_form_fields action hook, you can style new category input fields however you want, and link them to simple meta-data.
Note –
You may update the attributes of current taxonomy objects by calling wp_update_term. This function lets us reset the name, slug, and term_group of a taxonomy object, and attach that object to additional attributes (taxonomy, description, parent).
As pointed out by R’phael Spindel below, there are various action hooks that allow you to link into wp_update_term. However, based on the current implementation of wp_update_term it will be difficult to inject our own data into the database update calls.
- edit_terms – which hooks in before name, slug, term_group are updated.
- edited_terms – which hooks in after name, slug, term_group are updated.
- edit_term_taxonomy – which hooks in before term_id, taxonomy, description, parent are updated.
- edited_term_taxonomy – which hooks in after term_id, taxonomy, description, parent are updated.
- edit_term, edit_category – which hooks in before cleaning the taxonomy cache.
- edited_term, edited_category – which hooks in after cleaning the taxonomy cache.
