ファイルをダウンロードさせるメソッド

ファイルをダウンロードさせる関数です。

<?php
function output_file($file, $name, $mime_type='')
{
 /*
 This function takes a path to a file to output ($file), 
 the filename that the browser will see ($name) and 
 the MIME type of the file ($mime_type, optional).
 
 If you want to do something on download abort/finish,
 register_shutdown_function('function_name');
 */
 if(!is_readable($file)) die('File not found or inaccessible!');
 
 $size = filesize($file);
 $name = rawurldecode($name);
 
 /* Figure out the MIME type (if not specified) */
 $known_mime_types=array(
 	"pdf" => "application/pdf",
 	"txt" => "text/plain",
 	"html" => "text/html",
 	"htm" => "text/html",
	"exe" => "application/octet-stream",
	"zip" => "application/zip",
	"doc" => "application/msword",
	"xls" => "application/vnd.ms-excel",
	"ppt" => "application/vnd.ms-powerpoint",
	"gif" => "image/gif",
	"png" => "image/png",
	"jpeg"=> "image/jpg",
	"jpg" =>  "image/jpg",
	"php" => "text/plain"
 );
 
 if($mime_type==''){
	 $file_extension = strtolower(substr(strrchr($file,"."),1));
	 if(array_key_exists($file_extension, $known_mime_types)){
		$mime_type=$known_mime_types[$file_extension];
	 } else {
		$mime_type="application/force-download";
	 };
 };
 
 @ob_end_clean(); //turn off output buffering to decrease cpu usage
 
 // required for IE, otherwise Content-Disposition may be ignored
 if(ini_get('zlib.output_compression'))
  ini_set('zlib.output_compression', 'Off');
 
 header('Content-Type: ' . $mime_type);
 header('Content-Disposition: attachment; filename="'.$name.'"');
 header("Content-Transfer-Encoding: binary");
 header('Accept-Ranges: bytes');
 
 /* The three lines below basically make the 
    download non-cacheable */
 header("Cache-control: private");
 header('Pragma: private');
 header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
 
 // multipart-download and download resuming support
 if(isset($_SERVER['HTTP_RANGE']))
 {
	list($a, $range) = explode("=",$_SERVER['HTTP_RANGE'],2);
	list($range) = explode(",",$range,2);
	list($range, $range_end) = explode("-", $range);
	$range=intval($range);
	if(!$range_end) {
		$range_end=$size-1;
	} else {
		$range_end=intval($range_end);
	}
 
	$new_length = $range_end-$range+1;
	header("HTTP/1.1 206 Partial Content");
	header("Content-Length: $new_length");
	header("Content-Range: bytes $range-$range_end/$size");
 } else {
	$new_length=$size;
	header("Content-Length: ".$size);
 }
 
 /* output the file itself */
 $chunksize = 1*(1024*1024); //you may want to change this
 $bytes_send = 0;
 if ($file = fopen($file, 'r'))
 {
	if(isset($_SERVER['HTTP_RANGE']))
	fseek($file, $range);
 
	while(!feof($file) && 
		(!connection_aborted()) && 
		($bytes_send<$new_length)
	      )
	{
		$buffer = fread($file, $chunksize);
		print($buffer); //echo($buffer); // is also possible
		flush();
		$bytes_send += strlen($buffer);
	}
 fclose($file);
 } else die('Error - can not open file.');
 
die();
}	
 
/*********************************************
			Example of use
**********************************************/	
 
/* 
Make sure script execution doesn't time out.
Set maximum execution time in seconds (0 means no limit).
*/
set_time_limit(0);	
$file_path='that_one_file.txt';
output_file($file_path, 'some file.txt', 'text/plain');
?>

なお、readfile() and fpassthru()を使うと２ＭＢしか転送しない不具合があったため、
下記の関数を用意しました。

<?php
function readfile_chunked($filename,$retbytes=true) {
    $chunksize = 1*(1024*1024); // how many bytes per chunk
    $buffer = '';
    $cnt =0;
    // $handle = fopen($filename, 'rb');
    $handle = fopen($filename, 'rb');
    if ($handle === false) {
        return false;
    }
    while (!feof($handle)) {
        $buffer = fread($handle, $chunksize);
        echo $buffer;
        if ($retbytes) {
            $cnt += strlen($buffer);
        }
    }
        $status = fclose($handle);
    if ($retbytes && $status) {
        return $cnt; // return num. bytes delivered like readfile() does.
    }
    return $status;

} 
?>