Show parent-child relationship for categories in the wordpress admin

Question

How can I show child categories under there parent category in the wordpress admin? On a post the format of the category box would look like this:

Category 1

• Sub-Category 1.1
• Sub-Category 1.2

Category 2

Answer 1

EDIT:

On a post page, the categories are already seen in hierarchical manner but with checkboxes. So, I have assumed that you have to show list of all the categories/subcategories somewhere in the admin panel in following format.

• Category 1
  • Sub-Category 1.1
  • Sub-Category 1.2
• Category 2

So, presentation is upto you, I have just given logic to pull the necessary data i.e. list of all the categories along with subcategories.

    $arg1 = array(
        'parent'                   => 0,
        'orderby'                  => 'name',
        'hide_empty'               => 0,
        'pad_counts'               => false 
        );

    $categories = get_terms('category', $arg1);  //or use your custom taxonomy name

    if( !empty($categories) && is_array($categories) ){

      echo '<ul>'; 

      foreach($categories as $cat){

        echo '<li>'.$cat->name;

        $arg2 = array(
                        'child_of'                 => $cat->term_id,
                        'orderby'                  => 'name',
                        'hide_empty'               => 0,
                        'pad_counts'               => false 
                    );

        $sub_categories = get_terms('category', $arg2); //or use your custom taxonomy name

        if(!empty($sub_categories) && is_array($sub_categories)){

          echo '<ul>';       

          foreach($sub_categories as $scat){

              echo '<li>'.$scat->name.'</li>';
          }
      echo '</ul>';
      }
      echo '</li>';
      }
    echo '</ul>';
    }

Answer 2

use this code for solving your problem.

<?php 
 $args = array( 'orderby' =>'name',
                'texonomy' =>'category',
                'child_of' =>0,
                'parent' =>0 );

        $cats = get_categories($args);
        foreach ($cats as $cat) {
             echo $cat->name;
 $arg = array('orderby' => 'name',
             'child_of' =>0,
              'parent' =>$cat->term_id);
            $sub_cats =get_categories($arg);

                foreach ($sub_cats as $sub) {
                    echo '<hr><br>';
                    echo '<h3>'.$sub->name.'</h3>';
                    echo '<hr><br>';
                    $args = array(
                            'post_type' => 'post',
                            'tax_query' => array(
                                array(
                                    'taxonomy' => 'category',
                                    'terms'    => $sub->term_id,
                                ),
                            ),
                        );

                    $query = new WP_query( $args);
                    //echo "<pre>"; print_r($query); echo "</pre>";
                    while($query->have_posts()) : $query->the_post();
                    echo "<br>";
                    the_title();
                    echo "<br>";
                    the_content();
                    endwhile;
                echo "<hr>";
                }
        }
 ?>