public function callFunction($url, $postData, $method, header='')
{
  $maxRetryTimes = 3;
  $curl = curl_init();
  /******初始化请求参数start******/
  if(strtoupper($method) !== 'GET' && $postData){
    curl_setopt($curl, CURLOPT_POSTFIELDS, json_encode($postData));
  }elseif (strtoupper($method) === 'GET' && $postData){
    $url .= '"http://php.net/manual/en/function.curl-setopt-array.php" rel="external nofollow" >http://php.net/manual/en/function.curl-setopt-array.php ，最终使用了CURLOPT_WRITEFUNCTION参数设置了on_curl_write，该函数将会1s中被回调1次。



$ch = curl_init();
$options = array(CURLOPT_URL    => 'http://www.php.net/',
CURLOPT_HEADER    => false,
CURLOPT_HEADERFUNCTION  => 'on_curl_header',
CURLOPT_WRITEFUNCTION  => 'on_curl_write'
);


最终我的实现片段：


function on_curl_write($ch, $data)
{
  $pid = getmypid();
  $downloadSizeRecorder = DownloadSizeRecorder::getInstance($pid);
  $bytes = strlen($data);
  $downloadSizeRecorder->downloadData .= $data;
  $downloadSizeRecorder->downloadedFileSize += $bytes;
//  error_log(' on_curl_write '.$downloadSizeRecorder->downloadedFileSize." > {$downloadSizeRecorder->maxSize} \n", 3, '/tmp/hyb.log');
  //确保已经下载的内容略大于最大限制
  if (($downloadSizeRecorder->downloadedFileSize - $bytes) > $downloadSizeRecorder->maxSize) {
    return false;
  }
  return $bytes; //这个不正确的返回，将会报错，中断下载 "errno":23,"errmsg":"Failed writing body (0 != 16384)"
}


DownloadSizeRecorder是一个单例模式的类，curl下载时记录大小，实现返回下载内容的md5等。


class DownloadSizeRecorder
{
  const ERROR_FAILED_WRITING = 23; //Failed writing body
  public $downloadedFileSize;
  public $maxSize;
  public $pid;
  public $hasOverMaxSize;
  public $fileFullName;
  public $downloadData;
  private static $selfInstanceList = array();
  public static function getInstance($pid)
  {
    if(!isset(self::$selfInstanceList[$pid])){
      self::$selfInstanceList[$pid] = new self($pid);
    }
    return self::$selfInstanceList[$pid];
  }
  private function __construct($pid)
  {
    $this->pid = $pid;
    $this->downloadedFileSize = 0;
    $this->fileFullName = '';
    $this->hasOverMaxSize = false;
    $this->downloadData = '';
  }
  /**
   * 保存文件
   */
  public function saveMaxSizeData2File(){
    if(empty($resp_data)){
      $resp_data = $this->downloadData;
    }
    $fileFullName = '/tmp/http_'.$this->pid.'_'.time()."_{$this->maxSize}.download";
    if($resp_data && strlen($resp_data)>0)
    {
      list($headerOnly, $bodyOnly) = explode("\r\n\r\n", $resp_data, 2);
      $saveDataLenth = ($this->downloadedFileSize < $this->maxSize) "htmlcode">

……
curl_setopt($ch, CURLOPT_WRITEFUNCTION, 'on_curl_write');//设置回调函数
……
$pid = getmypid();
$downloadSizeRecorder = DownloadSizeRecorder::getInstance($pid);
$downloadSizeRecorder->maxSize = $size_limit;
……
//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();


到这里，踩了一个坑。增加了on_curl_write后，$response会返回true，导致后面取返回内容的时候异常。好在已经实时限制了下载的大小，用downloadData来记录了已经下载的内容，直接可以使用。


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


总结
以上所述是小编给大家介绍的php使用curl下载指定大小的文件，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对网站的支持！