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 $return;
	        }
	    }else{
	        $return = '';
	    }    
	    return $return;
	
}