// Oluşturma Sayfasına Ekle
add_action( 'category_add_form_fields', 'add_category_field', 10, 2 );
function add_category_field( $taxonomy ) { ?>
  <div class="form-field term-group">
    <label for="category-custom-description">Açıklama</label>
    <textarea rows="5" id="category-custom-description" name="category-custom-description"></textarea>
  </div>
<?php }

// Oluşturma Sayfasında Güncelleme
add_action( 'created_category', 'save_category_field', 10, 2 );
function save_category_field ( $term_id, $tt_id ) {
  if( isset( $_POST['category-custom-description'] ) && '' !== $_POST['category-custom-description'] ){
    $posts = $_POST['category-custom-description'];
    add_term_meta( $term_id, 'category-custom-description', $posts, true );
  }
}

// Düzenleme Sayfasına Ekle
add_action( 'category_edit_form_fields', 'edit_category_fields', 10, 2 );
function edit_category_fields($term, $taxonomy ) {
  $description = get_term_meta( $term->term_id, 'category-custom-description', true );
  ?>
  <tr class="form-field">
    <th scope="row"><label for="category-custom-description">Açıklama</label></th>
    <td>
      <textarea row="5" name="category-custom-description" id="category-custom-description"><?php echo $description; ?></textarea>
    </td>
  </tr>
<?php }

// Düzenleme Sayfasında Güncelleme
add_action( 'edited_category', 'updated_category_fields', 10, 2 );
function updated_category_fields ( $term_id, $tt_id ) {
  if( isset( $_POST['category-custom-description'] ) && '' !== $_POST['category-custom-description'] ){
    $description = $_POST['category-custom-description'];
    update_term_meta ( $term_id, 'category-custom-description', $description );
  } else {
    update_term_meta ( $term_id, 'category-custom-description', '' );
  }
}