How to write in new database table?

[DrByte]

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

zen_db_perform('table', $sql_data_array);

That does the same as:

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

So, you're duplicating your efforts.

When i press the submit button i get blank page.
Where is the mistake?

Here's a tutorial on finding your mistakes that cause blank pages: https://www.zen-cart.com/tutorials/index.php?article=82