Código PHP:
<?php
...
// Conexión a la BD
...
$conexion = mysql_connect($servidor, $usuario, $clave) or die(mysql_error());
mysql_select_db($basedatos, $conexion) or die(mysql_error());
$query = "SELECT name, type, size, content " .
"FROM upload WHERE id = '5'";
$result = mysql_query($query) or die('Error, query failed');
list($name, $type, $size, $content) = mysql_fetch_array($result);
header("Content-length: $size");
header("Content-type: $type");
header("Content-Disposition: attachment; filename=$name");
echo $content;
exit;
?> 
