php使用curl下载指定大小的文件实例代码

……
curl_setopt($ch, CURLOPT_WRITEFUNCTION, 'on_curl_write');//设置回调函数
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$pid = getmypid();
$downloadSizeRecorder = DownloadSizeRecorder::getInstance($pid);
$downloadSizeRecorder->maxSize = $size_limit;
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//发起curl请求
$response = curl_exec($ch);
……
//保存文件，返回md5
$downloadSizeRecorder->saveMaxSizeData2File(); //保存
$downloadFileMd5 = $downloadSizeRecorder->returnFileMd5();
$downloadedfile_size = $downloadSizeRecorder->returnSize();
$downloadSizeRecorder->deleteFile();

if($response === true){
  $response = $downloadSizeRecorder->downloadData;
}