Display success message after downloading CSV - php

Question

I have developed a small Wordpress Plugin to download as a CSV file users' data from the database.
Everything works fine, although I am having issues figuring out how to display a success message.
Below the code of the method that takes care of the data export:
/*
* Export CSV File
*/
public function export_CSV()
{
if ($this->users) {
$fileName = "Export_users_" . date("Y-m-d_H:i:s", time());
$fileName = $fileName.".csv";
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header('Content-Description: File Transfer');
header('Content-Encoding: UTF-8');
header("Content-type: application/csv;charset=UTF-8");
header("Content-Disposition: attachment; filename={$fileName}");
header("Expires: 0");
header("Pragma: public");
echo "\xEF\xBB\xBF"; // UTF-8 BOM
$fh = #fopen( 'php://output', 'w' );
$headerDisplayed = false;
foreach ($this->users as $user) {
if($user) {
$user_meta = get_user_meta($user->data->ID);
//Push user meta into $user array
foreach($user_meta as $key => $var)
{
$user->data->$key = trim($var[0]);
}
//convert object in array;
$usersArray = (array)$user->data;
// Add a header row if it hasn't been added yet
if ( $headerDisplayed == false ) {
// Use the keys from $directory as the titles
fputcsv($fh, array_keys($usersArray));
$headerDisplayed = true;
}
// Put the data into the stream
fputcsv($fh,$usersArray);
}//end if
}//end foreach
// Close the file
fclose($fh);
// Users exported successfully
$this->response = "Users exported successfully!";
// Make sure nothing else is sent
exit;
} else {
// No results found
$this->response = "Sorry, no results found!";
}
}
I have to use exit otherwise the CSV file will contain all the html of the page. Is there a way to run a javascript file to update the message in the front end?
Thanks in advance!

Answer 1

First of all:
Put the download details in a separate page. You can only send the headers once, that's one of the reasons why you can't print html after sending the csv header.
Secondly you could then create an if/else statement for if the function has succeeded. and if it did you could add some JS code like the example below:
if($download = true) {
echo "<script> alert('Download succesfull!'); </script>";
}
else {
echo "<script> alert('Download failed!'); </script>";
}
Tho i'm not sure if it could work like above since it's an server event. Another possible solution would be by creating a ServerEventCheck.

Answer 2

I came up with a solution by passing the response message as a variable in the header.
$this->response = "Users downloaded Successfully!";
header("Location:?page=export-users&response=".$this->response);
and then retrieve it like so:
<?php if(isset($_GET['response'])){ ?>
<div class="updated notice">
<p><?php echo __( $_GET['response']);?></p>
</div><!--error notice-->
<?php } ?>