How to write in new database table in zen cart

Question

I have created a new database table with the name 'table'. Now i'm trying the following code to write the data into the fields:

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

$F1 = $_POST['F1'];
$F2 = $_POST['F2'];
$F3 = $_POST['F3'];
$F4 = $_POST['F4'];

$sql_data_array = array('F1' => zen_db_prepare_input($_POST['F1']),
'F2' => zen_db_prepare_input($_POST['F2']));

zen_db_perform('table', $sql_data_array);

$db->Execute("insert into requests (F1, F2, F3, F4) values ('".$F1."', '"$F2."', '".$F3."', '".$F4. "')");
}

When i press the submit button i get blank page. It means something wrong with my code. Where is the mistake? Please help me out.