Download file through an AJAX call in PHP

While AJAX isn't ideal for file downloads due to browser security restrictions, you can trigger file downloads from PHP using JavaScript redirection methods like window.location or by creating downloadable links dynamically.

Using window.location for File Download

The simplest approach is to redirect the browser to a PHP script that serves the file ?

function downloadFile(fileId) {
    window.location.href = '/download.php?file=' + fileId;
}

The corresponding PHP download script ?

<?php
// download.php
$fileId = $_GET['file'] ?? '';
$filePath = '/uploads/' . basename($fileId) . '.pdf';

if (file_exists($filePath)) {
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename="' . basename($filePath) . '"');
    header('Content-Length: ' . filesize($filePath));
    readfile($filePath);
    exit;
} else {
    http_response_code(404);
    echo 'File not found';
}
?>

AJAX with Dynamic Link Creation

For better user experience, create a temporary download link via AJAX ?

function downloadViaAjax(fileId) {
    fetch('/generate-download-link.php', {
        method: 'POST',
        headers: {'Content-Type': 'application/x-www-form-urlencoded'},
        body: 'file=' + fileId
    })
    .then(response => response.json())
    .then(data => {
        if (data.success) {
            const link = document.createElement('a');
            link.href = data.downloadUrl;
            link.download = data.filename;
            link.click();
        }
    });
}

The PHP script that generates the secure download URL ?

<?php
// generate-download-link.php
header('Content-Type: application/json');

$fileId = $_POST['file'] ?? '';
$token = bin2hex(random_bytes(16));

// Store token in session or database
$_SESSION['download_tokens'][$token] = $fileId;

echo json_encode([
    'success' => true,
    'downloadUrl' => '/secure-download.php?token=' . $token,
    'filename' => 'document.pdf'
]);
?>

Comparison

Conclusion

Use window.location for simple file downloads or AJAX with dynamic link creation for better UX. Always validate file paths and implement proper security measures to prevent unauthorized access.