Are there any best practices for securely offering a file download using PHP?

When offering a file download using PHP, it is important to ensure that the download link is secure to prevent unauthorized access to the file. One best practice is to store the files outside of the web root directory and use PHP to handle the download process, verifying permissions before allowing the download to proceed. 

<?php
// Check if the user is authenticated and has permission to download the file
if($user_authenticated && $user_has_permission) {
    $file_path = '/path/to/file.pdf';
    
    // Make sure the file exists
    if(file_exists($file_path)) {
        // Set headers to force download and prevent caching
        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename="' . basename($file_path) . '"');
        header('Content-Length: ' . filesize($file_path));
        
        // Read the file and output it to the browser
        readfile($file_path);
        exit;
    } else {
        echo 'File not found.';
    }
} else {
    echo 'You do not have permission to download this file.';
}
?>

Keywords

file download PHP security authentication encryption

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