php – curl获取远程文件并同时强制下载

我正在尝试获取远程文件并强制同时将其下载到用户.
我无法粘贴代码,代码太长.但curl函数有效,但问题是它没有输出任何东西,直到它首先获取远程文件然后它强制下载到用户.

我用它来告诉curl返回一个回调

curl_setopt($ch,CURLOPT_READFUNCTION,'readCallback');

现在在我的readCallback函数中我这样做：

function readCallback($curl,$stream,$maxRead){
    $read = fgets($stream,$maxRead);
    echo $read;
    return $read;
}

但它不会返回任何它等待直到获取远程文件完成.

<?php
$file = 'http://example.com/somefile.mp3';
download($file,2000);

/*
Set Headers
Get total size of file
Then loop through the total size incrementing a chunck size
*/
function download($file,$chunks){
    set_time_limit(0);
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-disposition: attachment; filename='.basename($file));
    header('Cache-Control: must-revalidate,post-check=0,pre-check=0');
    header('Expires: 0');
    header('Pragma: public');
    $size = get_size($file);
    header('Content-Length: '.$size);

    $i = 0;
    while($i<=$size){
        //Output the chunk
        get_chunk($file,(($i==0)?$i:$i+1),((($i+$chunks)>$size)?$size:$i+$chunks));
        $i = ($i+$chunks);
    }

}

//Callback function for CURLOPT_WRITEFUNCTION,This is what prints the chunk
function chunk($ch,$str) {
    print($str);
    return strlen($str);
}

//Function to get a range of bytes from the remote file
function get_chunk($file,$start,$end){
    $ch = curl_init();
    curl_setopt($ch,CURLOPT_URL,$file);
    curl_setopt($ch,CURLOPT_RANGE,$start.'-'.$end);
    curl_setopt($ch,CURLOPT_BINARYTRANSFER,1);
    curl_setopt($ch,CURLOPT_WRITEFUNCTION,'chunk');
    $result = curl_exec($ch);
    curl_close($ch);
}

//Get total size of file
function get_size($url){
    $ch = curl_init();
    curl_setopt($ch,$url);
    curl_setopt($ch,CURLOPT_FOLLOWLOCATION,true);
    curl_setopt($ch,CURLOPT_RETURNTRANSFER,CURLOPT_HEADER,CURLOPT_NOBODY,true);
    curl_exec($ch);
    $size = curl_getinfo($ch,CURLINFO_CONTENT_LENGTH_DOWNLOAD);
    return intval($size);
}
?>

（编辑：安卓应用网）

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