PMA\libraries\Index::addColumns PHP Method

    public function addColumns($columns)
    {
        $_columns = array();
        if (isset($columns['names'])) {
            // coming from form
            // $columns[names][]
            // $columns[sub_parts][]
            foreach ($columns['names'] as $key => $name) {
                $sub_part = isset($columns['sub_parts'][$key]) ? $columns['sub_parts'][$key] : '';
                $_columns[] = array('Column_name' => $name, 'Sub_part' => $sub_part);
            }
        } else {
            // coming from SHOW INDEXES
            // $columns[][name]
            // $columns[][sub_part]
            // ...
            $_columns = $columns;
        }
        foreach ($_columns as $column) {
            $this->addColumn($column);
        }
    }