PHP字符串关键字过滤

/**
 * 字符串关键字过滤
 * @param $find         要查找的值
 * @param $replace      替换 find 中的值的值
 * @param $subject      被搜索的字符串
 * @return bool|mixed   返回替换后的字符串
 */
public function keyword_replace($find, $replace, $subject)
{
    if(is_array($find) && !empty($find)){
        $subject = str_replace(' ', '',$subject); //过滤空格
        foreach($find as $v){
            $len = mb_strlen($v, 'utf-8');
            $x = '';
            for($i = 0; $i < $len; $i++){
                $x .= $replace;
            }
            $str2 = str_replace($v, $x, $subject);
            $subject = $str2;
        }
        return $str2;
    }else{
        return $subject;
    }
}