php用header()实现文件下载功能

function download($file_url,$new_name=''){
	if(!isset($file_url)||trim($file_url)==''){
		return '500';
	}
	if(!file_exists($file_url)){//检查文件是否存在
		return '404';
	}
	$file_name=basename($file_url);
	$file_type=explode('.',$file_url);
	$file_type=$file_type[count($file_type)-1];
	$file_name=trim($new_name=='')?$file_name:urlencode($new_name).'.'.$file_type;
	//输入文件标签phpernote
	header("Content-type: application/octet-stream");
	header("Accept-Ranges: bytes");
	header("Accept-Length: ".filesize($file_url));
	header("Content-Disposition: attachment; filename=".$file_name);
	//