function my_Categ_tree($catId, $depth){
    $depth .= \'-\';  $output =\'\';
    $args = \'hierarchical=1&taxonomy=category&hide_empty=0&parent=\';    $categories = get_categories($args . $catId);
    if(count($categories)>0){
        foreach ($categories as $category) {
            $selected = ($cat->term_id=="22") ? " selected": "";
            $output .=  \'<option value="\'.$category->cat_ID.\'" \'.$selected .\'>\'.$depth.$category->cat_name.\'</option>\';
            $output .=  my_Categ_tree($category->cat_ID,$depth);
        }
    }
    return $output;
}

echo my_Categ_tree(0,\'\');

<?php

    // Get top level categories and list them
    $args = array(\'orderby\' => \'name\', \'parent\' => 0);
    $categories = get_categories( $args );

    foreach ($categories as $category) {

    echo $category->cat_name . \'<br>\';

    $args2 = array(\'orderby\' => \'name\', \'parent\' => $category->cat_ID);
    $subcategories = get_categories( $args2 );

    echo \'<ul>\';

    // While listing top level categories
    // list their child categories
    foreach ($subcategories as $subcategory) {
        echo \'<li>\' . $subcategory->cat_name . \'</li>\';
    }

    echo \'</ul>\';

    }
?>

如果要显示自定义分类法的所有类别和子类别，请使用此代码并确保提供分类法的slug。

function ow_categories_with_subcategories( $taxonomy ) {

    // Get the top categories that belong to the provided taxonomy (the ones without parent)
    $categories = get_terms( 
        array(
            \'taxonomy\'   => $taxonomy,
            \'parent\'     => 0, // <-- No Parent
            \'orderby\'    => \'term_id\',
            \'hide_empty\' => true // <!-- change to false to also display empty ones
        )
    );
    ?>
    <div>
        <?php
        // Iterate through all categories to display each individual category
        foreach ( $categories as $category ) {

            $cat_name = $category->name;
            $cat_id   = $category->term_id;
            $cat_slug = $category->slug;

            // Display the name of each individual category
            echo \'<h3>Category: \' . $cat_name . \' - ID: \' . $cat_id . \' - Slug: \' . $cat_slug  . \'</h3>\'; 


            // Get all the subcategories that belong to the current category
            $subcategories = get_terms(
                array(
                    \'taxonomy\'   => $taxonomy,
                    \'parent\'     => $cat_id, // <-- The parent is the current category
                    \'orderby\'    => \'term_id\',
                    \'hide_empty\' => true
                )
            );
            ?>
            <div>
                <?php
                // Iterate through all subcategories to display each individual subcategory
                foreach ( $subcategories as $subcategory ) {

                    $subcat_name = $subcategory->name;
                    $subcat_id   = $subcategory->term_id;
                    $subcat_slug = $subcategory->slug;

                    // Display the name of each individual subcategory with ID and Slug
                    echo \'<h4>Subcategory: \' . $subcat_name . \' - ID: \' . $subcat_id . \' - Slug: \' . $subcat_slug  . \'</h4>\';
                }
                ?>
            </div>
            <?php
        }
        ?>
    </div>
    <?php
}
ow_categories_with_subcategories( \'the_name_of_your_taxonomy\' );

我有非常4行的解决方案，它显示类别和子类别及其帖子数量。

$cats = get_terms(\'category\');
foreach ($cats as $cat) {
  echo $cat->name . "<br>" . "(" . $cat->count . ")"; 
}