获取微信昵称时 过滤特殊字符

/**
* $str  微信昵称
**/
    public function filter($str) {     
        if($str){
            $name = $str;
            $name = preg_replace("/xEE[x80-xBF][x80-xBF]|xEF[x81-x83][x80-xBF]/", "", $name);
            $name = preg_replace("/xE0[x80-x9F][x80-xBF]‘.‘|xED[xA0-xBF][x80-xBF]/S","?", $name);
            $return = json_decode(preg_replace("#(\ud[0-9a-f]{3})#ie","",json_encode($name)));
            if(!$return){
                return $this->jsonName($return);
            }
        }else{
            $return = "";
        }    
        return $return;

}