PHP Script para exportar consulta a excel

[mortisdj]

Pues esto, pero esta mal por todas partes, xD Además de que no se como hacer para que salga un pequeño formulario para poner elegir la fecha, vamos, en ese caso se que ha de ser algo similar a esto...

SELECT * FROM tutabla WHERE (date BETWEEN '$date1' AND '$date2')

Pero no se como aplicarlo en el ejemplo que pongo a continuación, al igual que a la hora de hacer un select en plan desplegable para el product_reference, :S

Código:

$conexion = new mysqli(mi_server, mi_username, password, database);

if(isset($_POST['submitExport'])) {

    $fp = fopen("import/users.csv","w");
    $separador = ";";

    $linea = 'g.firstname'.$separador.'g.lastname'.$separador.'g.foundus'.$separador.'product_quantity'."\n"; 
    fwrite($fp, $linea);

    $result = $conexion->query("SELECT CONCAT_WS(  ' ', g.firstname, g.lastname, g.foundus ) AS Cliente, g.lastname AS Centro, n.`product_name` AS Producto, n.`product_quantity` AS Cantidad FROM  `ps_orders` o LEFT JOIN  `ps_customer` g ON g.`id_customer` = o.`id_customer` LEFT JOIN  `ps_order_detail` n ON n.`id_order` = o.`id_order` WHERE o.date_upd BETWEEN  '2014-01-01' AND  '2014-12-31' AND n.`product_reference` =  "PB001" LIMIT 0 , 30");
    if ($result->num_rows > 0) {
        while ($row_users = $result->fetch_assoc()) {                
            $linea = $row_users['g.firstname'].$separador.$row_users['g.lastname'].$separador.$row_users['g.foundus'].$separador.$row_users['product.quantity']."\n"; 
            fwrite($fp, $linea);
        }
    }

    $message_export = '<p><a href="import/users.csv"><b>Ver ventas .csv</b></a></p>';

    fclose($fp);    
}

<fieldset>
    <legend>Exportar Ventas</legend>
    <form method="post" action="index.php">
        <input type="submit" value="Export .CSV file" name="submitExport">
        <?php if (!empty($message_export)) echo $message_export; ?>
    </form>
</fieldset>
<fieldset>
    <legend>Usuarios registrados</legend>
    <table width="490px" cellpadding="0" cellspacing="5">
        <tr>
            <td>Cliente</td>
            <td>Centro</td>
            <td>Cantidad</td>
        </tr>
           <?php
        $result = $conexion->query("SELECT CONCAT_WS(  ' ', g.firstname, g.lastname, g.foundus ) AS Cliente, g.lastname AS Centro, n.`product_name` AS Producto, n.`product_quantity` AS Cantidad FROM  `ps_orders` o LEFT JOIN  `ps_customer` g ON g.`id_customer` = o.`id_customer` LEFT JOIN  `ps_order_detail` n ON n.`id_order` = o.`id_order` WHERE o.date_upd BETWEEN  '2014-01-01' AND  '2014-12-31' AND n.`product_reference` =  "PB001" LIMIT 0 , 30");
        if ($result->num_rows > 0) {
            while ($row_users = $result->fetch_assoc()) {  
                echo '<tr>';
                echo '<td>'.$row_users['g.firstname, g.lastname'].'</td>';
                echo '<td>'.$row_users['g.foundus'].'</td>';
                echo '<td>'.$row_users['product_quantity'].'</td>';
                echo '</tr>';
            }
        }       
        ?>        
    </table>
</fieldset>