PHP本地文件&远程文件下载

/**
 * @description  文件下载 支持本地和远程文件
 * @param        $fileUrl  本地文件绝对路径 OR 远程文件地址
 * @param string $fileName 下载保存的文件名
 */
function download_file($fileUrl, $fileName = ''){
    if($fileName == ''){
        $filename = explode('/', str_replace(DIRECTORY_SEPARATOR, '/', $fileUrl));
        $filename = end($filename);
    }else{
        $filename = $fileName;
    }
    //直接下载本地文件
    if (!headers_sent()) {
        if (file_exists($fileUrl) && !empty($filename)) {
            $fileOpen = fopen($fileUrl, 'rb');
            $fileSize = filesize($fileUrl);
            header("Cache-Control: public");//缓存控制
            header("Content-Type: application/octet-stream");
            header("Accept-Ranges: bytes");
            header("Content-Length: " . $fileSize);
            header('Access-Control-Expose-Headers: Content-Disposition');
            header("Content-Disposition: attachment; filename=" . $filename);
            $chunk_size = 4096; // 针对大文件，规定每次读取文件的字节数为4096字节，直接输出数据
            $sum_buffer = 0; //总的缓冲的字节数
            ob_start(); // 开启缓冲区
            //只要没到文件尾，就一直读取
            while (!feof($fileOpen) && $sum_buffer < $fileSize) {
                echo fread($fileOpen, $chunk_size);
                $sum_buffer += $chunk_size;
                ob_flush(); // 刷新PHP缓冲区到Web服务器
                flush(); // 刷新Web服务器缓冲区到浏览器
            }
            ob_end_clean(); // 关闭缓冲区
            fclose($fileOpen);
            exit;
        }
    }else{
        exit;
    }
    //下载远程文件到本地
    $localTemporaryDir = FILE_UPLOAD.'uploads/temporary/';//此处注意改成自己项目配置的文件下载目录
    if(!is_dir($localTemporaryDir)){
        mkdir($localTemporaryDir,0777,true);
    }
    $localFile = $localTemporaryDir . $fileName;
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_HEADER, FALSE);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 900);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);
    curl_setopt($ch, CURLOPT_BINARYTRANSFER, TRUE);
    $file = curl_exec($ch);
    curl_close($ch);
    if(!strpos($file, '<Error>')){
        @unlink($localFile);
        file_put_contents($localFile, $file);
    }
    if (file_exists($localFile)) {
        download_file($localFile);//调用自己
    }
}