获取微信服务器的录音，下载amr，转换mp3，一气呵成！

$serverId = $_POST['serverId'];//传过来的serverID，也就是media_id

$path = "./sound/";   //保存路径

$outPath = "./record/";  //输出路径

$access_token = getAccessToken();

if(!is_dir($path)){
    mkdir($path);
}
//https://developers.weixin.qq.com/doc/offiaccount/Asset_Management/Get_temporary_materials.html
//高清语音素材获取接口
//$url = "https://api.weixin.qq.com/cgi-bin/media/get/jssdk?access_token={$access_token}&media_id={$serverId}";
//普通素材获取
$url = "https://api.weixin.qq.com/cgi-bin/media/get?access_token={$access_token}&media_id={$serverId}";

$file_amr = $openid.time().".amr";
$file_mp3 = $openid.time().".mp3";

$amr = $outPath.$file_amr;
$mp3 = $path.$file_mp3;
downAndSaveFile($url,$outPath.$file_amr);
$duration = 0;
$state='';


if(file_exists($amr))
{
    // echo "当前目录中，文件".$amr."存在";
    $command = "/usr/local/ffmpeg_sources/FFmpeg/ffmpeg -i $amr $mp3";
    exec($command,$out,$state);
    if($state == 0){
       echo "转换成功";
    }else{
    	echo "转换失败";
    }

}





//获取Token
function getAccessToken() {
    //  access_token 应该全局存储与更新，以下代码以写入到文件中做示例
    $data = json_decode(file_get_contents("./access_token.json"));
    if ($data->expire_time < time()) {
        $appid = "xxxxxxxxxxx";  //你自己的appid
        $appsecret = "xxxxxxxxxx";  //你自己的appsecret
        $url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid={$appid}&secret={$appsecret}";
        $res = json_decode(httpGet($url));
        $access_token = $res->access_token;
        if ($access_token) {
            $data->expire_time = time();
            $data->access_token = $access_token;
            $fp = fopen("./access_token.json", "w");
            fwrite($fp, json_encode($data));
            fclose($fp);
        }
    }
    else {
        $access_token = $data->access_token;
    }
    return $access_token;
}

//HTTP get 请求
function httpGet($url) {
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_TIMEOUT, 500);
    curl_setopt($curl, CURLOPT_URL, $url);

    $res = curl_exec($curl);
    curl_close($curl);

    return $res;
}

//根据URL地址，下载文件
function downAndSaveFile($url,$savePath){
    ob_start();
    readfile($url);
    $img = ob_get_contents();
    ob_end_clean();
    $size = strlen($img);
    $fp = fopen($savePath, 'a');
    fwrite($fp, $img);
    fclose($fp);
}