Render view after image file is downloaded in Yii - php

Question

public function actionViewDownload(){
// some in internal processing php commands (no echo)
exec($command); // command to be executed compulsary
$file = "/images/sample.jpg"; // some images file
if (file_exists($file)) {
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename='.basename($file));
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($file));
readfile($file);
}
$this->render('view',array('data'=>$data)); // render the other view of the controller after/during download.
}
I need to execute a command, then download the image file and after or during downloading render, the view.
If I render the view before downloading it prompts "Header cannot be modified. Headers already sent"
and if I render the view after the download then view is now shown on browser but the file gets downloaded.
My question here is that how can I achieve three tasks : execution of the command (this must be first), render and download.

Answer 1

By the looks of it you are trying to do something like sourceforge does when you ask to download a project where the deliverable is pushed to the user as the page is rendered.
I am assuming that the exec generates the image.
You really need to split this into 2 actions:
public function actionViewDownload(){
// some in internal processing php commands (no echo)
exec($command); // command to be executed compulsory
$file = "/images/sample.jpg"; // some images file
$this->render('view',array(
'data'=>$data,
'img'=>$file)
);
}
Then the view contains something like:
<img src="<?php echo controller/getdeliverible?file=$img; ?>"/>
which in turn calls:
public function actionGetDeliverible($file){
if (file_exists($file)) {
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename='.basename($file));
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($file));
readfile($file);
}
}
My above code is rough (you'll have to fill it in properly) but you get the idea. Basically as the view is rendered the image will pop up and ask you to save it. It will appear to the user that both things are happening together.
The nice thing about doing it this way is that you can do something after you have read the image to the user like delete it if it was a temporary file so it can't be downloaded again.