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wp_popular_terms_checklist() WP 2.5.0

Retrieve a list of the most popular terms from the specified taxonomy.

If the $echo argument is true then the elements for a list of checkbox <input> elements labelled with the names of the selected terms is output. If the $post_ID global isn't empty then the terms associated with that post will be marked as checked.

Hooks in function
Return

Array. List of popular term IDs.

Usage

wp_popular_terms_checklist( $taxonomy, $default, $number, $echo );
$taxonomy(string) (required)
Taxonomy to retrieve terms from.
$default(int)
Not used.
Default: 0
$number(int)
Number of terms to retrieve.
Default: 10
$echo(true/false)
Optionally output the list as well.
Default: true

Code of wp popular terms checklist: wp-admin/includes/template.php VER 5.0.3

<?php
function wp_popular_terms_checklist( $taxonomy, $default = 0, $number = 10, $echo = true ) {
	$post = get_post();

	if ( $post && $post->ID )
		$checked_terms = wp_get_object_terms($post->ID, $taxonomy, array('fields'=>'ids'));
	else
		$checked_terms = array();

	$terms = get_terms( $taxonomy, array( 'orderby' => 'count', 'order' => 'DESC', 'number' => $number, 'hierarchical' => false ) );

	$tax = get_taxonomy($taxonomy);

	$popular_ids = array();
	foreach ( (array) $terms as $term ) {
		$popular_ids[] = $term->term_id;
		if ( !$echo ) // Hack for Ajax use.
			continue;
		$id = "popular-$taxonomy-$term->term_id";
		$checked = in_array( $term->term_id, $checked_terms ) ? 'checked="checked"' : '';
		?>

		<li id="<?php echo $id; ?>" class="popular-category">
			<label class="selectit">
				<input id="in-<?php echo $id; ?>" type="checkbox" <?php echo $checked; ?> value="<?php echo (int) $term->term_id; ?>" <?php disabled( ! current_user_can( $tax->cap->assign_terms ) ); ?> />
				<?php
				/** This filter is documented in wp-includes/category-template.php */
				echo esc_html( apply_filters( 'the_category', $term->name, '', '' ) );
				?>
			</label>
		</li>

		<?php
	}
	return $popular_ids;
}