Habari\Vocabulary::add_term PHP Method

    public function add_term($term, $target_term = null, $before = false)
    {
        $new_term = $term;
        if (is_string($term)) {
            $new_term = new Term(array('term_display' => $term));
        }
        $new_term->vocabulary_id = $this->id;
        $ref = 0;
        DB::begin_transaction();
        // If there are terms in the vocabulary, work out the reference point
        if (!$this->is_empty()) {
            if ($this->hierarchical) {
                // If no parent is specified, put the new term after the last term
                if (null == $target_term) {
                    $ref = DB::get_value('SELECT mptt_right FROM {terms} WHERE vocabulary_id=? ORDER BY mptt_right DESC LIMIT 1', array($this->id));
                } else {
                    if (!$before) {
                        $ref = $target_term->mptt_right - 1;
                    } else {
                        $ref = $target_term->mptt_left - 1;
                    }
                }
            } else {
                // If no before_term is specified, put the new term after the last term
                if (!$before) {
                    $ref = DB::get_value('SELECT mptt_right FROM {terms} WHERE vocabulary_id=? ORDER BY mptt_right DESC LIMIT 1', array($this->id));
                } else {
                    $ref = $target_term->mptt_left - 1;
                }
            }
            // Make space for the new node
            $params = array('vocab_id' => $this->id, 'ref' => $ref);
            $res = DB::query('UPDATE {terms} SET mptt_right=mptt_right+2 WHERE vocabulary_id=:vocab_id AND mptt_right>:ref', $params);
            if (!$res) {
                DB::rollback();
                return false;
            }
            $res = DB::query('UPDATE {terms} SET mptt_left=mptt_left+2 WHERE vocabulary_id=:vocab_id AND mptt_left>:ref', $params);
            if (!$res) {
                DB::rollback();
                return false;
            }
        }
        // Set the right and left appropriately
        $new_term->mptt_left = $ref + 1;
        $new_term->mptt_right = $ref + 2;
        // Insert the new node
        $result = $new_term->insert();
        if ($result) {
            DB::commit();
            return $new_term;
        } else {
            DB::rollback();
            return false;
        }
    }