要为页面或帖子添加选项框，您需要使用add_meta_boxes 行动

 //Register Meta Box
 function register_meta_box() {
      add_meta_box(
          \'meta-box-id\',
          __( \'MetaBox Title\', \'text-domain\' ), 
          \'meta_box_callback\', 
          \'post\', 
          \'advanced\', 
          \'high\' 
     );
 }
 add_action( \'add_meta_boxes\', \'register_meta_box\');

  //Add field
  function meta_box_callback( $post_id ) {

 $output = \'<label for="title_field">\'. esc_html__(\'Title Field\', \'text-domain\') .\'</label>\';
 $title_field = get_post_meta( $post_id->ID, \'title_field\', true );
 $output .= \'<input type="text" name="title_field" id="title_field" class="title_field" value="\'. esc_attr($title_field) .\'" />\';

     echo $output;
 }

// Save meta field
add_action(\'save_post\', \'save_meta_field\');

function save_meta_field($post_id){
      // Check nonce, sanitize field
      update_post_meta($post_id, \'title_field\', $_POST[\'title_field\']);
}

您将发现有关add_meta_boxes here

希望有帮助

我认为，最简单的方法是：Advanced custom fields plugin