Why PDF files stored in mysql database became damaged/corrupted when downloaded?

Question

I'm creating page where users can upload/download pdf files which is stored in mysql database, the problem that when I download a file, it becomes corrupted/damaged

NP: data of the file stored as blob in the database.

Below is my code:

        // Gather all required data
        $name = $dbLink->real_escape_string($_FILES['uploaded_file']['name']);
        $mime = $dbLink->real_escape_string($_FILES['uploaded_file']['type']);
        $data = $dbLink->real_escape_string(file_get_contents($_FILES           ['uploaded_file']['tmp_name']));
        $size = intval($_FILES['uploaded_file']['size']);

        // Create the SQL query
        $query = "
            INSERT INTO `file` (
                `name`, `mime`, `size`, `data`, `created`
            )
            VALUES (
                '{$name}', '{$mime}', {$size}, '{$data}', NOW()
            )";

        // Execute the query
        $result = $dbLink->query($query);

        // Check if it was successfull
        if($result) {
            echo 'Success! Your file was successfully added!';
        }
        else {
            echo 'Error! Failed to insert the file'
               . "<pre>{$dbLink->error}</pre>";
        }
    }
    else {
        echo 'An error accured while the file was being uploaded. '
           . 'Error code: '. intval($_FILES['uploaded_file']['error']);
    }

    // Close the mysql connection
    $dbLink->close();
}
else {
    echo 'Error! A file was not sent!';
}

download code: 
 // Fetch the file information
        $query = "
            SELECT `mime`, `name`, `size`, `data`
            FROM `file`
            WHERE `id` = {$id}";
        $result = $dbLink->query($query);

        if($result) {
            // Make sure the result is valid
            if($result->num_rows == 1) {
            // Get the row
                $row = mysqli_fetch_assoc($result);

                // Print headers
                //header('Content-Type: application/pdf');
                header("Content-Type: application/force-download"); 
                header("Pragma: public"); 
                header("Content-Description: File Transfer");
                header("Content-Type: ".$row['mime']);
                header("Content-Length: ".$row['size']);
                header("Content-Disposition: attachment; filename=".$row['name']);
                header("Content-Transfer-Encoding: binary");
                header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
                // Print data
                @readfile($row['data']);
            }
            else {
                echo 'Error! No file exists with that ID.';
            }

            // Free the mysqli resources
            @mysqli_free_result($result);
        }
        else {
            echo "Error! Query failed: <pre>{$dbLink->error}</pre>";
        }
        @mysqli_close($dbLink);
    }
}
else {
    echo 'Error! No ID was passed.';
}

Bad idea to store the file contents in the database, see http://stackoverflow.com/questions/3748/storing-images-in-db-yea-or-nay — James T, Mar 15 '12 at 02:33
@Bubby4j it's a school project, so I don't have the choice :S — Samer El Gendy, Mar 15 '12 at 02:40

score 2 · Accepted Answer · answered Mar 15 '12 at 07:00

Not the way. Mysqli is not the way either. You always have a choice, tell your teacher there is no value in this approach. Why not store a jpg in a mysql database? Cause there is a better way - store the link in the database, store the .jpg on web. Same with a PDF. If you must peruse, look at how web based editors like ckedit store data (another wrong approach.), and also look at dompdf code.google.com/p/dompdf/ to get an idea of what breaks the pdf format.

Why is mysqli a bad idea? mySql is what it is. mySql tries to make it something else that is better done with other methods, otherwise mysql would do it.

Why PDF files stored in mysql database became damaged/corrupted when downloaded?

1 Answers1