It's time to create new or re-design your websites to bring it to the next level.
This guide will show you how to make checkboxlist – inspired by Jordan Ivanov:
The first thing you need to do is to modify K2 and Joomla! core files. All files are attached to this post.
1. In /libraries/joomla/html/html/select.php after line 125
2. In /administrator/components/com_k2/models/extrafield.php in lines: 60, 298, 224
3. In /administrator/components/com_k2/views/extrafield/view.html.php in line 47
4. In /administrator/components/com_k2/views/extrafields/view.html.php in line 72
5. In /media/k2/assets/js/k2.js in line 523
6. In /components/com_k2/models/item.php in line 1035
7.In /administratorllanguage/en-GB/en-BG.com_k2.ini in line 445
Next, you unpack in some safe place, at the same time, you check all changes after uploading all files into your server.
Note: We discourage hacking K2 or Joomla! core.