framework/db/SqlToken.php
public function offsetSet($offset, $token)
    {
        $token->parent = $this;
        if ($offset === null) {
            $this->_children[] = $token;
        } else {
            $this->_children[$this->calculateOffset($offset)] = $token;
        }
        $this->updateCollectionOffsets();
    }
public function offsetSet($offset, $token)
    {
        $token->parent = $this;
        if ($offset === null) {
            $this->_children[] = $token;
        } else {
            $this->_children[$this->calculateOffset($offset)] = $token;
        }
        $this->updateCollectionOffsets();
    }
Adds a child token to the token.
This method is required by the SPL [[\ArrayAccess]] interface.
It is implicitly called when you use something like `$token[$offset] = $child;`.
@param int|null $offset child token offset.
@param SqlToken $token token to be added.