_str = $str; $this->_keyword = $keyword; } public function __toString() { $str = $this->_str; if (!$str) { return ''; } if (!empty($this->_keyword)) { $keywords = explode(" ", $this->_keyword); foreach ($keywords as $keyword) { $str = preg_replace('#('.$keyword.')#i', '$1', $str); } } return $str; } }