How use CURLOPT_WRITEFUNCTION when download a file by CURL

My Class for download file direct from a link:

MyClass{

          function download($link){
                ......
                $ch = curl_init($link);
                curl_setopt($ch, CURLOPT_FILE, $File->handle);
             开发者_运维百科   curl_setopt($ch,CURLOPT_WRITEFUNCTION , array($this,'__writeFunction'));
                curl_exec($ch);
                curl_close($ch);
                $File->close();
                ......

            }

          function __writeFunction($curl, $data) {
                return strlen($data);            
          } 
}

I want know how to use CRULOPT_WRITEFUNCTION when download file. Above code if i remove line:

curl_setopt($ch,CURLOPT_WRITEFUNCTION , array($this,'__writeFunction'));

Then it will run good, i can download that file.But if i use CURL_WRITEFUNCTION option i can't download file.

I know this is an old question, but maybe my answer will be of some help for you or someone else. Try this:

function get_write_function(){
    return function($curl, $data){
        return strlen($data);
    }
}

I don't know exactly what you want to do, but with PHP 5.3, you can do a lot with the callback. What's really great about generating a function in this way is that the values passed through the 'use' keyword remain with the function afterward, kind of like constants.

function get_write_function($var){
    $obj = $this;//access variables or functions within your class with the object variable
    return function($curl, $data) use ($var, $obj) {
        $len = strlen($data);
        //just an example - you can come up with something better than this:
        if ($len > $var){
            return -1;//abort the download
        } else {
            $obj->do_something();//call a class function
            return $len;
        }
    }
}

You can retrieve the function as a variable as follows:

function download($link){
    ......
    $var = 5000;
    $write_function = $this->get_write_function($var);
    $ch = curl_init($link);
    curl_setopt($ch, CURLOPT_FILE, $File->handle);
    curl_setopt($ch, CURLOPT_WRITEFUNCTION , $write_function);
    curl_exec($ch);
    curl_close($ch);
    $File->close();
    ......

}

That was just an example. You can see how I used it here: Parallel cURL Request with WRITEFUNCTION Callback. I didn't actually test all of this code, so there may be minor errors. Let me know if you have problems, and I'll fix it.

<?php 
$ch = curl_init();
curl_setopt($ch, CURLOPT_BUFFERSIZE, 8096);
curl_setopt($ch, CURLOPT_BINARYTRANSFER, true);
curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt($ch, CURLOPT_URL, 'http://blog.ronnyristau.de/wp-content/uploads/2008/12/php.jpg');

$content = curl_exec($ch);

curl_close($ch);

$out = fopen('/tmp/out.png','w');
if($out){
    fwrite($out, $content);
    fclose($out);
}

Why do you use curl to download a file? Is there a special reason? You can simply use fopen and fread

I have written a small class for it.

<?php
class Utils_FileDownload  {
    private $source;
    private $dest;
    private $buffer;
    private $overwrite;
    public function __construct($source,$dest,$buffer=4096,$overwrite=false){
        $this->source = $source;
        $this->dest   = $dest;
        $this->buffer = $buffer; 
        $this->overwrite = $overwrite;
    }
    public function download(){
        if($this->overwrite||!file_exists($this->dest)){
            if(!is_dir(dirname($this->dest))){mkdir(dirname($this->dest),0755,true);}
            if($this->source==""){
                $resource = false;
                Utils_Logging_Logger::getLogger()->log("source must not be empty.",Utils_Logging_Logger::TYPE_ERROR);
            }
            else{ $resource = fopen($this->source,"rb"); }
            if($this->source==""){
                $dest = false;
                Utils_Logging_Logger::getLogger()->log("destination must not be empty.",Utils_Logging_Logger::TYPE_ERROR);
            }
            else{ $dest     = fopen($this->dest,"wb"); }
            if($resource!==false&&$dest!==false){
                while(!feof($resource)){
                    $read = fread($resource,$this->buffer);
                    fwrite($dest,$read,$this->buffer);
                }
                chmod($this->dest,0644);
                fclose($dest); fclose($resource);
                return true;
            }else{
                 return false;   
            }
        }else{
            return false;
        }
    }
}

It seems like cURL uses your function instead of writing to the request once CURLOPT_WRITEFUNCTION is specified.

So the correct solution would be :

MyClass{

      function download($link){
            ......
            $ch = curl_init($link);
            curl_setopt($ch, CURLOPT_FILE, $File->handle);
            curl_setopt($ch,CURLOPT_WRITEFUNCTION , array($this,'__writeFunction'));
            curl_exec($ch);
            curl_close($ch);
            $File->close();
            ......

        }

      function __writeFunction($curl, $data) {
            echo $data;
            return strlen($data);            
      } 
}

This can also handle binary files as well.