PHP output contents of file

attachment.php

<?php
    $file_path = "/full/path/of/the/file.doc";
    if ( file_exists($file_path) ) {
        $file_name = basename($file_path);
        $mime_type = mime_content_type($file_path);
        $file_size = filesize($file_path);

        header('Content-Description: File Transfer');
        header("Content-Type: {$mime_type}");
        header("Content-Disposition: attachment; filename=\"{$file_name}\"");
        header("Expires: 0");
        header("Cache-Control: must-revalidate");
        header("Pragma: public");
        header("Content-Length: {$file_size}");
        readfile($file_name); // Esto imprime el contenido del archivo
    }
    else {
        http_response_code(404);
        echo 'File does not exist.';
    }

    exit;