遠(yuǎn)程下載錄音文件到本地，結(jié)果播放內(nèi)容為空

遠(yuǎn)程URL ：http://cloudcallcenter-online.oss-cn-shanghai.aliyuncs.com/record/cc278f9c-104c-44d3-ac3a-0d5a85f127b6/152626432510500080329349.wav?Expires=1527220202&OSSAccessKeyId=LTAIvKWEr4DoFSqz&Signature=T2dBY2elShoYunkp4fKY1d3PC3U%3D

代碼：`public function download($url, $dir)

{
    $ch = curl_init($url);
    $fp = fopen($dir, "wb");
    curl_setopt($ch, CURLOPT_FILE, $fp);
    curl_setopt($ch, CURLOPT_HEADER, 0);
    $res = curl_exec($ch);
    curl_close($ch);
    fclose($fp);
}`

大家在跑腳本的時(shí)候下載錄音是怎么下，還望賜教.