wp_dropdown_categories() will list by id by default. It utilizes get_terms() as well, and provides a hook to toward the end if you wish to filter the html of $output further than the parameters allow. (I’ve added the source below).
It has the following parameters:
- ‘show_option_all’
(string) Text to display for showing all categories.
- ‘show_option_none’
(string) Text to display for showing no categories.- ‘option_none_value’
(string) Value to use when no category is selected.- ‘orderby’
(string) Which column to use for ordering categories. See get_terms() for a list of accepted values. Default ‘id’ (term_id).- ‘order’
(string) Whether to order terms in ascending or descending order. Accepts ‘ASC’ or ‘DESC’. Default ‘ASC’.- ‘pad_counts’
(bool) See get_terms() for an argument description. Default false.- ‘show_count’
(bool|int) Whether to include post counts. Accepts 0, 1, or their bool equivalents. Default 0.- ‘hide_empty’
(bool|int) Whether to hide categories that don’t have any posts. Accepts 0, 1, or their bool equivalents. Default 1.- ‘child_of’
(int) Term ID to retrieve child terms of. See get_terms(). Default 0.- ‘exclude’
(array|string) Array or comma/space-separated string of term ids to exclude. If $include is non-empty, $exclude is ignored. Default empty array.- ‘echo’
(bool|int) Whether to echo or return the generated markup. Accepts 0, 1, or their bool equivalents. Default 1.- ‘hierarchical’
(bool|int) Whether to traverse the taxonomy hierarchy. Accepts 0, 1, or their bool equivalents. Default 0.- ‘depth’
(int) Maximum depth. Default 0.- ‘tab_index’
(int) Tab index for the select element. Default 0 (no tabindex).- ‘name’
(string) Value for the ‘name’ attribute of the select element. Default ‘cat’.- ‘id’
(string) Value for the ‘id’ attribute of the select element. Defaults to the value of $name.- ‘class’
(string) Value for the ‘class’ attribute of the select element. Default ‘postform’.- ‘selected’
(int|string) Value of the option that should be selected. Default 0.- ‘value_field’
(string) Term field that should be used to populate the ‘value’ attribute of the option elements. Accepts any valid term field: ‘term_id’, ‘name’, ‘slug’, ‘term_group’, – ‘term_taxonomy_id’, ‘taxonomy’, ‘description’, ‘parent’, ‘count’. Default ‘term_id’.- ‘taxonomy’
(string|array) Name of the category or categories to retrieve. Default ‘category’.- ‘hide_if_empty’
(bool) True to skip generating markup if no categories are found. Default false (create select element even if no categories are found).- ‘required’
(bool) Whether the element should have the HTML5 ‘required’ attribute. Default false.
function wp_dropdown_categories( $args="" ) {
$defaults = array(
'show_option_all' => '',
'show_option_none' => '',
'orderby' => 'id',
'order' => 'ASC',
'show_count' => 0,
'hide_empty' => 1,
'child_of' => 0,
'exclude' => '',
'echo' => 1,
'selected' => 0,
'hierarchical' => 0,
'name' => 'cat',
'id' => '',
'class' => 'postform',
'depth' => 0,
'tab_index' => 0,
'taxonomy' => 'category',
'hide_if_empty' => false,
'option_none_value' => -1,
'value_field' => 'term_id',
'required' => false,
);
$defaults['selected'] = ( is_category() ) ? get_query_var( 'cat' ) : 0;
// Back compat.
if ( isset( $args['type'] ) && 'link' == $args['type'] ) {
_deprecated_argument( __FUNCTION__, '3.0.0',
/* translators: 1: "type => link", 2: "taxonomy => link_category" */
sprintf( __( '%1$s is deprecated. Use %2$s instead.' ),
'<code>type => link</code>',
'<code>taxonomy => link_category</code>'
)
);
$args['taxonomy'] = 'link_category';
}
$r = wp_parse_args( $args, $defaults );
$option_none_value = $r['option_none_value'];
if ( ! isset( $r['pad_counts'] ) && $r['show_count'] && $r['hierarchical'] ) {
$r['pad_counts'] = true;
}
$tab_index = $r['tab_index'];
$tab_index_attribute="";
if ( (int) $tab_index > 0 ) {
$tab_index_attribute = " tabindex=\"$tab_index\"";
}
// Avoid clashes with the 'name' param of get_terms().
$get_terms_args = $r;
unset( $get_terms_args['name'] );
$categories = get_terms( $r['taxonomy'], $get_terms_args );
$name = esc_attr( $r['name'] );
$class = esc_attr( $r['class'] );
$id = $r['id'] ? esc_attr( $r['id'] ) : $name;
$required = $r['required'] ? 'required' : '';
if ( ! $r['hide_if_empty'] || ! empty( $categories ) ) {
$output = "<select $required name="$name" id='$id' class="$class" $tab_index_attribute>\n";
} else {
$output="";
}
if ( empty( $categories ) && ! $r['hide_if_empty'] && ! empty( $r['show_option_none'] ) ) {
/**
* Filters a taxonomy drop-down display element.
*
* A variety of taxonomy drop-down display elements can be modified
* just prior to display via this filter. Filterable arguments include
* 'show_option_none', 'show_option_all', and various forms of the
* term name.
*
* @since 1.2.0
*
* @see wp_dropdown_categories()
*
* @param string $element Taxonomy element to list.
*/
$show_option_none = apply_filters( 'list_cats', $r['show_option_none'] );
$output .= "\t<option value="" . esc_attr( $option_none_value ) . "" selected='selected'>$show_option_none</option>\n";
}
if ( ! empty( $categories ) ) {
if ( $r['show_option_all'] ) {
/** This filter is documented in wp-includes/category-template.php */
$show_option_all = apply_filters( 'list_cats', $r['show_option_all'] );
$selected = ( '0' === strval($r['selected']) ) ? " selected='selected'" : '';
$output .= "\t<option value="0"$selected>$show_option_all</option>\n";
}
if ( $r['show_option_none'] ) {
/** This filter is documented in wp-includes/category-template.php */
$show_option_none = apply_filters( 'list_cats', $r['show_option_none'] );
$selected = selected( $option_none_value, $r['selected'], false );
$output .= "\t<option value="" . esc_attr( $option_none_value ) . ""$selected>$show_option_none</option>\n";
}
if ( $r['hierarchical'] ) {
$depth = $r['depth']; // Walk the full depth.
} else {
$depth = -1; // Flat.
}
$output .= walk_category_dropdown_tree( $categories, $depth, $r );
}
if ( ! $r['hide_if_empty'] || ! empty( $categories ) ) {
$output .= "</select>\n";
}
/**
* Filters the taxonomy drop-down output.
*
* @since 2.1.0
*
* @param string $output HTML output.
* @param array $r Arguments used to build the drop-down.
*/
$output = apply_filters( 'wp_dropdown_cats', $output, $r );
if ( $r['echo'] ) {
echo $output;
}
return $output;
}