PHP download file from server from POST - php

Question

What began here: PHP finding file where post INCLUDES portion of filename
I am trying to finish with this question.
Basically, now that I am able to post a variable to a PHP process, then use that process to find a file in a directory, I now need to be able to download the file if it exists.
Quick recap, after the user has entered a voyage number and the datatable has returned a list of voyages, the user then clicks the link, which is where I'll begin the code:
$('.voyageFileCall').on('click', function()
{
var voyage = $(this).attr('data-voyage');
$.post('fileDownload.php', {voyage:voyage}, function(data)
{
// here is where I need to where either display the file doesn't exist
// or the file downloads
});
});
The process 'fileDownload.php' looks like this:
<?php
if($_POST['voyage'] == true)
{
$voyage = $_POST['voyage'];
$files = scandir("backup/");
if(count($files) > 0)
{
$fileFound = false;
foreach($files as $file)
{
if((preg_match("/\b$voyage\b/", $file) === 1))
{
// I'm guessing the download process should happen here
echo "File found: $file \n"; // <-- this is what I currently have
$fileFound = true;
}
}
if(!$fileFound) die("File $voyage doesn't exist");
}
else
{
echo "No files in backup folder";
}
}
?>
I tried to use the answer found here: Download files from server php
But I'm not exactly sure where I should put the headers, or if I need to use them at all.

Answer 1

The quick solution which i can suggest you is: return path to file if it is exist, and return false if file doesn't exist.
After that in your JS code you can check, if your "data" == false, you can throw an error "file doesn't exist", and if it is not "false", you can call document.location.href = data; - it will redirect your browser to the file and it will be downloaded

Answer 2

Why don't you simply use download attribute:
<?php
if($_POST['voyage'] == true)
{
$voyage = $_POST['voyage'];
$files = scandir("backup/");
if(count($files) > 0)
{
$fileFound = false;
foreach($files as $file)
{
if((preg_match("/\b$voyage\b/", $file) === 1))
{
// I'm guessing the download process should happen here
echo 'File found: <a href="' . $file . '" download>' . $file . '</a> \n'; // <-- this is what I currently have
$fileFound = true;
}
}
if(!$fileFound) die("File $voyage doesn't exist");
}
else
{
echo "No files in backup folder";
}
}
?>
If you really want to use JavasScript to start download then use style="display:none;" for <a> and then in JS just click it:
echo 'File found: <a id="myDownload" style="display:none;" href="' . $file . '" download>' . $file . '</a> \n';
and call it:
$('.voyageFileCall').on('click', function()
{
var voyage = $(this).attr('data-voyage');
$.post('fileDownload.php', {voyage:voyage}, function(data)
{
if(document.getElementById("myDownload")){
document.getElementById("myDownload").click();
}else{
console.log("file does not exist");
}
});
});