如何使用php中的“另存为”对话框将特定CSV文件从服务器下载到客户端？

Question

I have a file named CO2.csv on the server and I want the user through a button in a form to download and save it with a new file name to a whatever location in his hard drive.

this is the Html script of the button that calls the php code

 <form action="FCO2.php"  method="post" <?php if(empty($_SESSION["CO2"])){?>style="display:none"<?php } ?> >

    <input type="submit" value="Export to CSV" name="submit">

</form> 

And here is the FCO2.php

<?php

$file = 'temp/CO2temp.csv';

if(!$file)
{ // file does not exist
    die('file not found');
} 
else 
{
    header("Cache-Control: public");
    header("Content-Description: File Transfer");
    header("Content-Disposition: attachment; filename=$file");
    header("Content-Type: text/csv");
    header("Content-Transfer-Encoding: text/csv");

}
?>

But it didn't work, it always create an empty file and never copies the file that is located on the server.

Answer 1

oh your just missing a call to the actual file such as using readfile

so adding it in:

<?php

$file = 'temp/CO2temp.csv';

if(!$file)
{ // file does not exist
    die('file not found');
} 
else 
{
    header("Cache-Control: public");
    header("Content-Description: File Transfer");
    header("Content-Disposition: attachment; filename=$file");
    header("Content-Type: text/csv");
    header("Content-Transfer-Encoding: text/csv");
    readfile($file);
   exit;// good practice but if this is the whole file, its not needed

}
?>

Answer 2

You are outputting a pile of headers, but your PHP ends before you output the file.

You can use readfile to do that.