ohctech_p8/get_calibration_doc_link.php

<?php
include('includes/config/config.php');
include('includes/functions.php');
include('log_entry.php');

if (isset($_REQUEST['id'])) {
    $id = mysqli_real_escape_string($conn, $_REQUEST['id']);

    $sql = "SELECT bill_file,bill_file_name,bill_file_type FROM calibration_item_tbl WHERE calibration_id  = $id";

    error_log("doc query " . $sql);

    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        $row = $result->fetch_assoc();

        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename="' . $row['bill_file_name'] . '"');


        ob_clean();
        echo $row['bill_file'];
        die;
    } else {
        echo "Document not found";
    }
}